noun
old badger; veteran; old fox; schemer
Literally 'old badger', used figuratively for a seasoned, crafty person who is experienced and often sly. Can be neutral or slightly negative depending on context.
彼は業界の古狸で、誰も騙せない。
He's an old fox in the industry; nobody can fool him.
あの政治家はまさに古狸だ。
That politician is a real old hand.
Compound of 古 (old) and 狸 (raccoon dog, badger). In Japanese folklore, badgers (or raccoon dogs) are tricksters, so an old one is especially cunning.