Ask.com has bought a stable of Internet reference sites that includes Dictionary.com in its latest effort to distinguish itself from online search leader Google Inc. and other much larger rivals.

Besides Dictionary.com, Ask is picking up Thesaurus.com and Reference.com in its acquisition of Lexico Publishing Group LLC. Terms of the deal, set to be announced Thursday, aren’t being disclosed.

With the addition of the widely used reference tools, Ask hopes to make more money showing ads to people looking for answers to basic questions. “We want to ’super serve’ those people,” said Jim Safka, who runs Ask for its corporate parent, IAC/InterActiveCorp.