I. ˈ ̷ ̷| ̷ ̷ noun
Etymology: back (III) + wind
: a wind blowing onto the wrong side of a sail ; especially : one directed upon a mainsail by a wrongly trimmed jib
II. transitive verb
1. : to direct a backwind upon
a jib thus bellied is most apt to backwind the mainsail
2. : to sail to windward of (another sailing ship) so as to blanket or interfere with the wind
backwind his opponent in a yacht race