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Phrase(s): *on the tip of one’s tongue
Fig. [of a thought or idea] about to be said or almost remembered. (*Typically: be ~; have something ~.) • I have his name right on the tip of my tongue. I’ll think of it in a second. • John had the answer on the tip of his tongue, but Anne said it first.
McGrawhill's American Idioms And Phrasal Verbs