Any mark applied to a stamp to prevent its re-use in the post. Found in various forms including a postmark, pen cancellation, an overprint or manuscript addition denoting invalidation, eg. Cancelled, Specimen, Sample, Inutilizado, or mute cancellations (see Barred) or punched with holes (see Holed). A mute cancellation is a postmark void of inscription, letters, or figures. In U.S. referred to as a “killer.”