1. Not defended or capable of being defended
   - undefendable, undefended, open

See also: assail, assailability, vulnerable

• outstroke
• outswinger
• outtake
• outthrust
• outturn
• outvie
• outvote
• outwait
• outward
• outward-bound
• outward-developing
• outward-moving
• outwardly
• outwardness
• outwards
• outwear
• outweigh
• outweird
• outwit
• outwith
• outwork
• ouzel
• ouzo
• OV
• oval