Not having a good reason or valid explanation; not deserved or warranted.
From un- (not) + justified (from Latin justificare, meaning to make just or right). The prefix un- negates the idea that something has proper grounds.
In typography, 'unjustified' text means the right margin is ragged and uneven (not 'justified' or aligned), so the same word means totally different things to English teachers versus graphic designers.
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