na-adjective
seeming to want to say something; looking like one wants to speak
Describes a person's expression or manner that suggests they have something to say but are holding back. Often used with そうに or な.
彼女は何か言いたげな顔でこちらを見ていた。
She was looking at me with a face that seemed to want to say something.
彼は言いたげに口を開きかけたが、結局黙った。
He opened his mouth as if to say something, but in the end he stayed silent.
言いたい is the plain 'want to say' form, while 言いたげ describes the appearance of wanting to say something.
Formed from 言いたい (want to say) + げ (suffix indicating seeming or appearance). The げ suffix attaches to the stem of adjectives to express 'looking like' or 'seeming'.