Noun

1. a rotational bearing, any one of
   1. The short stubby bearings on either side of a cannon; a gudgeon
   2. A rotational bearing comprised of a rotating arc or ring sliding in the groove of a stationary arc. Used when you wish to have rotation without an axle. Used especially in table saw and band saws in order to tilt the blade or table respectively. The trunnion allows the angle between the blade and table to be adjusted while keeping the point where the blade passes through the table stationary.