Reem means attractive, smart-looking, or just seriously good. It was popularised by Joey Essex on TOWIE, so it’s got that Essex nightclub gloss, but people all over the UK use it now. You can drop it as a straight compliment or a bit of playful hype when your mate’s feeling themselves and needs feeding the ego.
"Bruv, you’re looking reem tonight. Fresh trim, clean creps, smelling peng. Stop gassing yourself and come for a cheeky Nando’s."