Messy means everything is out of place. Clothes on the floor, three mugs by the bed, a desk with no visible surface left.
It goes well past rooms. Messy handwriting is hard to read, messy hair has not seen a brush, and messy food is the kind you cannot eat without wearing some of it — a dripping burger, a ripe peach. Then there is the bigger use: a messy divorce, a messy resignation, a messy few weeks at work. That has nothing to do with tidiness. It means complicated, unpleasant and hard to sort out, with people left upset along the way. The noun is a mess, and the opposite is tidy or neat.
1adjectivemessyUntidy; with things left out of place.
“His room is messy but he knows where everything is.”
synonyms: untidy, cluttered
2adjectivemakingMaking dirt, spills or marks.
“Painting with small children is messy work.”
3adjectivecomplicatedComplicated, unpleasant and hard to resolve.
“It turned into a messy argument about money.”
Also accepted in games: untidy
Middle English
mesh — mash
English
mess
English, today
messy
From mess + -y. mess Perhaps a corruption of Middle English mesh (“mash”), compare muss, or derived from Etymology 2 "mixed foods, as for animals". Compare also Old English mes (“dung, excrement”).
Etymology from Wiktionary, CC BY-SA