past tense of realise (British spelling); became aware of or understood something; made something real or actual
from French 'réaliser', from 'réal' (real) + '-iser' suffix, meaning to make real, first used in English in 1610s
The British spell it 'realised' while Americans prefer 'realized' - it's one of those spelling differences that makes you realise how the same language can be delightfully different across the pond!
Complete word intelligence in one call. Free tier — 50 lookups/day.