the formation of a word by subtraction of an element from an existing word, or a word formed in this way, e.g. burgle from burglar
Some back-formations are very old: pea and cherry were both formed in the Middle English period when people removed what they believed to be a plural suffix from the forms pease and cherise, and grovel and sidle are long-established verbs created by back-formation from adjectives. In modern English, the great majority of back-formations are verbs formed from nouns