21-letter words containing p, e, r, i, n
- ulster unionist party — a Northern Irish political party advocating the maintenance of union with the UK
- uncertainty principle — the principle of quantum mechanics, formulated by Heisenberg, that the accurate measurement of one of two related, observable quantities, as position and momentum or energy and time, produces uncertainties in the measurement of the other, such that the product of the uncertainties of both quantities is equal to or greater than h/ 2 π, where h equals Planck's constant.
- west university place — a city in SE Texas.
- wet collodion process — a photographic process, in common use in the mid-19th century, employing a glass photographic plate coated with iodized collodion and dipped in a silver nitrate solution immediately before use.
- what price something? — what are the chances of something happening now?
- whip-and-tongue graft — a graft prepared by cutting both the scion and the stock in a sloping direction and inserting a tongue in the scion into a slit in the stock.
- white-crowned sparrow — a North American sparrow, Zonotrichia leucophrys, having black and white stripes on the head.
- white-knuckle paddler — an inexpert and timid canoeist.
- wholesale price index — an indicator of price changes in the wholesale market
- wilson's storm petrel — a small petrel, Oceanites oceanicus, that breeds in the Southern Hemisphere but ranges into the North Atlantic and Pacific oceans.
- workers' compensation — a government-sponsored insurance system, funded by contributions from employers, for compensating employees for injury or occupational disease suffered in connection with their employment
- xeroderma pigmentosum — a rare inherited disease characterized by sensitivity to ultraviolet light, exposure resulting in lesions and tumors of the skin and eyes.
- xfree86 project, inc. — (operating system, graphics) A non-profit organisation that produces XFree86, a freely redistributable implementation of the X Window System that runs on Unix and Unix-like operating systems and OS/2. The XFree86 Project has traditionally focused on Intel x86 based platforms (hence the "86"), but the current release supports other platforms.