1. a message that seems to convey no meaning

(synonym) nonsense , bunk , nonsensicality , hokum

(hypernym) message , content , subject matter , substance

(hyponym) absurdity , absurdness , ridiculousness

2. the quality of having great value or significance; "he resented the meaninglessness of the tasks they assigned him"

(antonym) meaningfulness

(hypernym) insignificance

(hyponym) inanity , senselessness , mindlessness , vacuity , pointlessness