na-adjective, noun
meaningless; nonsense; pointless
Describes something that lacks meaning, purpose, or value. Can be used for statements, actions, or situations. Often carries a negative or dismissive tone.
そんなことをしても無意味だ。
Doing that is pointless.
彼の説明はまったく無意味だった。
His explanation was completely meaningless.
意味不明 means 'unintelligible' or 'incomprehensible', stressing that something cannot be understood, whereas 無意味 simply states it has no meaning.
Compound of 無 (mu, 'without') and 意味 (imi, 'meaning'). The reading is the standard on'yomi for both characters.