(geomorphology) A geomorphologic unconformity marking a boundary between an upland region and a plane; sometimes marked by a series of waterfalls on rivers that cross it.

(baseball) The World Series.

The state of being prone to error. / (countable) An error-generating characteristic.

(informal) One who is gullible and easily duped. / (informal) A scapegoat.

(intransitive, figuratively) To be ignored.

A result of a test that shows as absent something that is present. / (statistics) A type II error (“accepting the null hypothesis when it is false”).

A result of a test that shows as present something that is absent. / (statistics) type I error

(intransitive) To collapse inwards. / (intransitive, military) Of a soldier, to get into position in a rank. / To come to an end; to terminate; to lapse. / To become operative.

The event of small airborne particles falling to the ground in significant quantities as a result of major industrial activity, volcano eruption, sandstorm, nuclear explosion, etc.

Synonym of falling out (“rift following a disagreement or quarrel”)