godan verb (-tsu), transitive verb
open wide; throw open; leave open
Used for doors, windows, and similar openings. Can mean either opening something fully or leaving it open. Often implies a deliberate, forceful, or complete action.
See also: 開け放す
窓を開け放って、新鮮な空気を入れた。
I threw open the window and let in fresh air.
He left the front door wide open.