The term "screwball" is an informal, slangy adjective that can be used to describe something or someone as being unconventional, eccentric, or just plain weird. It often implies a sense of humor or playfulness in the way it's used, and can suggest something that's offbeat, zany, or simply out-of-the-ordinary. The term has its roots in baseball, where "screwball" is a type of pitch thrown with an unusual arm motion that breaks sharply in the opposite direction from which it was thrown - hence the name!