abseil

Concise Oxford English Dictionary © 2008 Oxford University Press:
abseil /ˈabseɪl, -zʌɪl/

▶verb Brit. descend a near-vertical surface using a doubled rope running through a friction device or coiled round the body and fixed at a higher point.

– derivatives
abseiler noun,
abseiling noun.

– origin 1930s: from Ger. abseilen, from ab ‘down’ + Seil ‘rope’.