Open English Wordnet
Adjectives
(a)meaningless, nonmeaningfulhaving no meaning or direction or purpose“a meaningless endeavor”, “a meaningless life”, “a verbose but meaningless explanation”
(s)futile, ineffectual, otiose, unavailing, meaninglessproducing no result or effect“a futile effort”, “the therapy was ineffectual”, “an otiose undertaking”, “an unavailing attempt”