diff --git a/src/definitions/_types.ts b/src/definitions/_types.ts
index c3f5424..b6efeae 100644
--- a/src/definitions/_types.ts
+++ b/src/definitions/_types.ts
@@ -1,6 +1,36 @@
 import type {KeywordDefinition} from "ajv"
+import type {Transformation} from "./transform"
 
-export interface DefinitionOptions {
+export interface KeywordOptions {
+  /**
+   * Modifications to the "transform" keyword
+   */
+  transform?: {
+    /**
+     * Override existing transformations or add additional (new)
+     * @example // overrides existing "trim" transformation, if "trim" didn't exist, it would have been added
+     *   import { trim } from "@example-org/pkgName/example-trim"
+     *
+     *   transform: {
+     *     trim: {
+     *       transformation: trim,
+     *       modulePath: "@example-org/pkgName/example-trim",
+     *     }
+     *   }
+     *
+     *   // module "example.trim.ts" ("@example-org/pkgName/example-trim") exports a function "trim"
+     *   export const trim = (value: string) => value.trim()
+     * @end
+     */
+    [key: string]: {
+      transformation: Transformation
+      modulePath: string
+    }
+  }
+}
+export type KeywordsWithCustomization = keyof KeywordOptions
+
+export interface DefinitionOptions extends KeywordOptions {
   defaultMeta?: string | boolean
 }
 
diff --git a/src/definitions/transform.ts b/src/definitions/transform.ts
index af4ae29..808d766 100644
--- a/src/definitions/transform.ts
+++ b/src/definitions/transform.ts
@@ -1,7 +1,8 @@
 import type {CodeKeywordDefinition, AnySchemaObject, KeywordCxt, Code, Name} from "ajv"
+import type {DefinitionOptions} from "./_types"
 import {_, stringify, getProperty} from "ajv/dist/compile/codegen"
 
-type TransformName =
+type TransformationName =
   | "trimStart"
   | "trimEnd"
   | "trimLeft"
@@ -15,9 +16,9 @@ interface TransformConfig {
   hash: Record<string, string | undefined>
 }
 
-type Transform = (s: string, cfg?: TransformConfig) => string
+export type Transformation = (s: string, cfg?: TransformConfig) => string
 
-const transform: {[key in TransformName]: Transform} = {
+const builtInTransformations: {[key in TransformationName]: Transformation} = {
   trimStart: (s) => s.trimStart(),
   trimEnd: (s) => s.trimEnd(),
   trimLeft: (s) => s.trimStart(),
@@ -28,11 +29,13 @@ const transform: {[key in TransformName]: Transform} = {
   toEnumCase: (s, cfg) => cfg?.hash[configKey(s)] || s,
 }
 
-const getDef: (() => CodeKeywordDefinition) & {
-  transform: typeof transform
-} = Object.assign(_getDef, {transform})
+function getDef(opts?: DefinitionOptions): CodeKeywordDefinition {
+  const customTransformations = opts?.transform || {}
+  const availableTransformations = [
+    ...Object.keys(builtInTransformations),
+    ...Object.keys(customTransformations),
+  ]
 
-function _getDef(): CodeKeywordDefinition {
   return {
     keyword: "transform",
     schemaType: "array",
@@ -54,19 +57,32 @@ function _getDef(): CodeKeywordDefinition {
 
       function transformExpr(ts: string[]): Code {
         if (!ts.length) return data
-        const t = ts.pop() as string
-        if (!(t in transform)) throw new Error(`transform: unknown transformation ${t}`)
-        const func = gen.scopeValue("func", {
-          ref: transform[t as TransformName],
-          code: _`require("ajv-keywords/dist/definitions/transform").transform${getProperty(t)}`,
-        })
+        const t = ts.pop() as TransformationName | string
+        if (!availableTransformations.includes(t)) {
+          throw new Error(`transform: unknown transformation ${t}`)
+        }
+
+        const func = gen.scopeValue(
+          "func",
+          customTransformations[t] // eslint-disable-line @typescript-eslint/no-unnecessary-condition
+            ? {
+                ref: customTransformations[t].transformation,
+                code: _`require("${customTransformations[t].modulePath}")${getProperty(t)}`,
+              }
+            : {
+                ref: builtInTransformations[t as TransformationName],
+                code: _`require("ajv-keywords/dist/definitions/transform").transform${getProperty(
+                  t
+                )}`,
+              }
+        )
         const arg = transformExpr(ts)
         return cfg && t === "toEnumCase" ? _`${func}(${arg}, ${cfg})` : _`${func}(${arg})`
       }
     },
     metaSchema: {
       type: "array",
-      items: {type: "string", enum: Object.keys(transform)},
+      items: {type: "string", enum: availableTransformations},
     },
   }
 }
diff --git a/src/index.ts b/src/index.ts
index bb580fb..ca70720 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,30 +1,48 @@
+/* eslint-disable valid-jsdoc */ // this rule is deprecated and insists on adding type annotations that already exist in TypeScript
 import type Ajv from "ajv"
 import type {Plugin} from "ajv"
-import plugins from "./keywords"
+import type {DefinitionOptions} from "./definitions/_types"
+import keywords from "./keywords"
 
 export {AjvKeywordsError} from "./definitions"
 
-const ajvKeywords: Plugin<string | string[]> = (ajv: Ajv, keyword?: string | string[]): Ajv => {
-  if (Array.isArray(keyword)) {
-    for (const k of keyword) get(k)(ajv)
+/**
+ * @param ajv instance
+ * @param specificKeywords only these keywords to-be-added
+ * @param options modifications passed to keywords
+ * @returns ajv instance
+ */
+const ajvKeywords: Plugin<string | string[]> = (
+  ajv: Ajv,
+  specificKeywords?: string | string[],
+  options: DefinitionOptions = {}
+): Ajv => {
+  if (Array.isArray(specificKeywords)) {
+    for (const k of specificKeywords) addKeyword(ajv, k, options)
     return ajv
   }
-  if (keyword) {
-    get(keyword)(ajv)
+  if (specificKeywords) {
+    addKeyword(ajv, specificKeywords, options)
     return ajv
   }
-  for (keyword in plugins) get(keyword)(ajv)
+
+  for (const keyword in keywords) addKeyword(ajv, keyword, options)
   return ajv
 }
 
 ajvKeywords.get = get
 
 function get(keyword: string): Plugin<any> {
-  const defFunc = plugins[keyword]
+  const defFunc = keywords[keyword]
   if (!defFunc) throw new Error("Unknown keyword " + keyword)
   return defFunc
 }
 
+function addKeyword(ajv: Ajv, keyword: string, options: DefinitionOptions): void {
+  const defFunc = get(keyword)
+  defFunc(ajv, options)
+}
+
 export default ajvKeywords
 module.exports = ajvKeywords
 
diff --git a/src/keywords/transform.ts b/src/keywords/transform.ts
index d6335ec..5f5c1af 100644
--- a/src/keywords/transform.ts
+++ b/src/keywords/transform.ts
@@ -1,7 +1,8 @@
 import type {Plugin} from "ajv"
+import type {KeywordOptions} from "../definitions/_types"
 import getDef from "../definitions/transform"
 
-const transform: Plugin<undefined> = (ajv) => ajv.addKeyword(getDef())
+const transform: Plugin<KeywordOptions["transform"]> = (ajv, opts) => ajv.addKeyword(getDef(opts))
 
 export default transform
 module.exports = transform