also: がたいのよい
expression, i-adjective (yoi/ii class)
big and brawny; well-built; gigantic
Describes a person, especially a man, with a large, muscular, or imposing physique. Often used in casual or colloquial contexts.
あのガタイの良い男はボディーガードだ。
That big, brawny guy is a bodyguard.
彼はガタイが良いけど、実は優しい。
He's well-built, but actually gentle.
More formal and neutral; ガタイの良い is slangier and emphasizes a rugged, muscular build.
Refers specifically to a muscular, macho physique, often with a nuance of bodybuilding; ガタイの良い is broader and can just mean large-framed.
ガタイ is a colloquial term for body frame or build, possibly derived from 体 (からだ) with a shift in pronunciation. The exact origin is uncertain.