Entry 1 sense Webster, 1913 Gallicism · Gal·li·cism · IPA /ˈɡælɪsɪzəm/ 01 n. A mode of speech peculiar to the French; a French idiom; also, in general, a French mode or custom. 1. A mode of speech peculiar to the French; a French idiom; also, in general, a French mode or custom.