English

Adjective

walk-in ‎(not comparable)

1. (of a place) that people may enter without a prior appointment
   • 2014, Ruzwana Bashir, "The untold story of how a culture of shame perpetuates abuse. I know, I was a victim", The Guardian, 29 August 2014:

     On multiple occasions, beginning when she was 12, Sara went to her local GP and to walk-in clinics wearing her hijab to get the morning-after pill.

2. (of a thief) that gains access through unlocked doors
3. (of a defector etc) that walks into an embassy etc unannounced
4. (US, of a cinema) not a drive-in
5. (of a room) entered without an intervening passage

Noun

walk-in ‎(plural walk-ins)

1. a walk-in room or closet
2. a walk-in defector etc.
   • 2007 April 10, "Who Killed Ashraf Marwan?," The New York Times (retrieved 18 September 2015):

     Still, a rapidly formed working group of Mossad wise men debated the risk in dealing with a walk-in, a volunteer who shows up bearing gifts."

3. (parapsychology) A person whose original soul has departed the body and been replaced with another.
4. A customer who visits a restaurant, hair salon, etc. without a reservation.
   • 1996, Kazuo Nishiyama, Welcoming the Japanese visitor: insights, tips, tactics (page 85)

     An astute manager will have a table or two set aside for important regular customers or demanding walk-ins.

References

• OED 2nd edition 1989