A noun that appears only in the plural and does not have a singular form. Plural, pluralia tantum. (A noun that appears only in the singular form--such as dirt--is known as singulare tantum.) See also: Plural Forms of Nouns.
Etymology:
A Latin phrase meaning "plural only"Examples and Observations:
- "Richard Lederer [in Crazy English, 1990] asks, 'Doesn't it seem just a little loopy that we can make amends but never just one amend; that no matter how carefully we comb through the annals of history, we can never discover just one annal; that we can never pull a shenanigan, be in a doldrum, or get a jitter, a willy, a delerium tremen, a jimjam, or a heebie-jeebie?' Lederer is alluding to pluralia tantum: Nouns that are always plural. Because they are not the result of pluralizing a singular, the complete plural form, -s and all, has to be stored in memory. Pluralia tantum in a sense are irregular regulars, and indeed they are happy to appear inside compounds: almsgiver (not almgiver), arms race (not arm race), blues rocker (not blue rocker, clothesbrush, Humanities department, jeans maker, newsmaker, oddsmaker, painstaking."
(Steven Pinker, Words and Rules, Basic Books, 1999) - "Let's take a look at other pluralia tantum in the pants/trousers family:
- Outergarments: pants (orig. pantaloons), trousers, slacks, breeches/britches, bloomers, jeans, dungarees, bell bottoms, chinos, tights, shorts, trunks, Bermudas (extended to brand names: Levis, 501s, Wranglers, Calvins)
- Undergarments: underpants, long johns, skivvies, drawers, panties, knickers, boxers, briefs, undies, tighty-whities (extended to brand names: BVDs, Fruit of the Looms, Jockeys)"


