Entry 1 sense Webster, 1913 Ratiocinate /(răsh`ĭ*ŏs"ĭ*nāt)/ · Ra·ti·oc·i·nate · IPA /ˌɹætiˈosəˌneɪt/ 01 v. i. To reason, esp. deductively; to offer reason or argument. 1. To reason, esp. deductively; to offer reason or argument.