godan verb (-ku), intransitive verb
grin broadly; smirk suggestively
Describes a wide, often suggestive or knowing grin, sometimes with a negative or sly connotation.
彼は何か企んでいるようににたついた。
He grinned broadly as if he were up to something.
彼女の顔がにたつくのを見て、何か隠
Seeing her face break into a suggestive grin, I felt she was hiding something.