walk-in

person who walks in without having an appointment

• “the emergency room was overrun with walk-ins”

an operative who initiates his own defection (usually to a hostile country) for political asylum

an assured victory (especially in an election)

a small room large enough to admit entrance

(of e.g. closets or refrigerators) extending very far enough back to allow a person to enter

• “a deep walk-in refrigerator”
• “walk-in closets”

enter by walking

• “She walks in at all hours, as if she lived here”