What is the meaning of Trunnion?

One of the short stubby bearings on either side of a cannon; a pintle.

A similar rotational bearing comprising a rotating arc or ring sliding in the groove of a stationary arc, used in machinery to allow a workpiece to be moved relative to a fixed tool.

A shaft, held by a bearing, at each end or side of a rotatable object.

A similar rotational bearing used in automotive suspensions.

Source: wiktionary.org