1. to handle; to deal with
(a) to operate; to use
E.g.: 扱い慣れた機械 (a machine one is used to handling)
(b) to take charge of; to deal with as a task
E.g.: 警察で扱う問題だ (a matter handled by the police)
(c) to treat; to regard
E.g.: 大人として扱う (to treat as an adult)
2. to thresh; to knead thoroughly