Immaterial, beside the point, and extraneous are all synonyms for irrelevant. Relevant and pertinent are antonyms of irrelevant. And here are 28 another word for irrelevant.
Beside the point, extraneous, immaterial, inapplicable, inapposite, inapt, inconsequential, insignificant, minor, negligible, neither here nor there, not germane, not pertinent, not to the point, of little account, of no matter/moment, off the subject, peripheral, petty, superficial, tangential, trifling, trivial, unconnected, unimportant, unrelated, and impertinent are all synonyms for irrelevant.
Irrelevant synonym page has a variety of synonyms that differ in length. 3 synonyms with 5, 11, and 13 letters and 1 synonym with 7, 8, 9, 14, 16, and 19 letters. 7 synonyms with 10 letters and 2 synonyms with 12, and 15 letters. For a total of 26 another word for irrelevant.
That detail is completely irrelevant today.
She dismissed the irrelevant comments quickly.
The question was deemed irrelevant during discussion.
His argument included many irrelevant points.