expression, ichidan verb
miss the target; be off the mark
Used both literally for missing a physical target and figuratively for remarks or guesses that are off the point.
矢が的を逸れてしまった。
The arrow missed the target.
彼の指摘は的を逸れている。
His point is off the mark.
的外れ is a noun/adjective meaning 'off the point' or 'irrelevant', while 的を逸れる is a verb phrase meaning 'to miss the target' or 'to be off the mark'.
Compound of 的 (target) + を (object marker) + 逸れる (to deviate, to miss). The verb 逸れる means to stray or go astray, so the phrase literally means 'to deviate from the target'.