You need to add a reference to the autocomplete.d.ts file e.g.:
/// <reference path="path/to/your/jquery.autocomplete.d.ts" />
Although I suspect that you are using the wrong definition file and should be using this one: https://github.com/borisyankov/DefinitelyTyped/blob/master/jqueryui/jqueryui.d.ts
It contains your required definition:
interface JQuery {
// ...
autocomplete(): JQuery;
autocomplete(methodName: string): JQuery;
autocomplete(methodName: 'close'): void;
autocomplete(methodName: 'destroy'): void;
autocomplete(methodName: 'disable'): void;
autocomplete(methodName: 'enable'): void;
autocomplete(methodName: 'search', value?: string): void;
autocomplete(methodName: 'widget'): JQuery;
autocomplete(options: JQueryUI.AutocompleteOptions): JQuery;
autocomplete(optionLiteral: string, optionName: string): any;
autocomplete(optionLiteral: string, options: JQueryUI.AutocompleteOptions): any;
autocomplete(optionLiteral: string, optionName: string, optionValue: any): JQuery;
// ...
}
Update: Quick useful solution Since you are using the bootstrap version, remove the reference to jquery.autocomplete.d.ts and jqueuryUI. And just have the following block before your code:
interface JQuery{
autocomplete(config:{source:string[];});
}