Slightly warm but not hot; lacking enthusiasm or energy; neither clearly supporting nor opposing something.
From Middle English 'leuk' (lukewarm) which likely comes from Germanic roots possibly related to 'leak' or 'lick'. The exact origin is uncertain, but the meaning developed around the 1300s.
Lukewarm is one of those perfect words where the meaning changed from purely physical (temperature) to emotional and political (lack of enthusiasm). The Bible uses it metaphorically—Jesus said the church of Laodicea was 'lukewarm' and he'd spit it out of his mouth!
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