To abseil is to go down a steep rock, a cliff, or the side of a building by sliding down a rope, while your feet push against the wall. You do not climb down with your hands on the rock the whole way; the rope holds you, and you let it out a little at a time. This is the usual word in British English. Though actually, in American English the same action is almost always called rappel (from French). Climbing films and US manuals will say rappel; UK instructors will say abseil. You can use it as a verb (“they abseiled down”) and as a noun for the act (“an abseil”). It is an outdoor-sport and rescue word, not an everyday city word — unless your work is ropes. It came into English from German, and the pieces are unusually clear: down + rope. It is not from sail on a boat, even though English makes it sound that way (AB-sale).

垂降