WordNet (r) 3.0 (2006):
lighten up v 1: make more cheerful; "the conversation lightened me up a bit" [syn: lighten, lighten up, buoy up] [ant: weigh down, weigh on] 2: become more cheerful; "after a glass of wine, he lightened up a bit" [syn: lighten, lighten up, buoy up] 3: make lighter or brighter; "The paint will brighten the room" [syn: brighten, lighten up, lighten] [ant: darken] 4: become lighter; "The room lightened up" [syn: lighten, lighten up] [ant: darken]