lighten up
verb- To make (something) or to become less serious and more cheerful or casual; to relax. · I wish he'd lighten up a bit and realize that we were only joking.· The mood at work has been tense, so he's looking for ways to lighten it up.
- To lighten (something): to decrease its weight. · Near-synonym: slim down· He can't get any more power out of it [his drag racer], so now he's looking for ways to lighten it up.
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