n (context|construction) A flexible cover of rubber or plastic, which may be preformed to a particular shape and used to protect a shaft, lever, switch, or opening from dust, dirt, moisture, etc.
n (US) A parking enforcement device used to immobilize a car until it can be towed or a fine is paid; a wheel clamp.
n A rubber bladder on the leading edge of an aircraft’s wing, which is inflated periodically to remove ice buildup. A deicing boot.
n (obsolete) A place at the side of a coach, where attendants rode; also, a low outside place before and behind the body of the coach.
n (computing) The act or process of bootstrapping; the starting or re-starting of a computing device.
v (computing) To bootstrap; to start a system, eg. a computer, by invoking its boot process or bootstrap.