(n.) A disused word or phrase; an archaism.

Encratism Friday Lenten fare Pythagoreanism Pythagorism Rechabitism Shakerism Spartan fare Stoicism abstainment abstemiousness abstinence anythingarianism asceticism avoidance banyan day celibacy chastity continence cop-out desuetude disuse eschewal evasion fast fence-sitting fish day fruitarianism gymnosophy impartiality independence mugwumpery mugwumpism nephalism neutralism neutrality nonalignment noncommitment nonemployment noninvolvement nonpartisanism nonprevalence nonuse nothingarianism obsolescence obsoleteness obsoletion obsoletism pensioning off plain living refraining refrainment retirement sexual abstinence simple diet spare diet strict neutrality superannuation teetotalism the pledge total abstinence unprevalence vegetarianism