18-letter words containing s, p, o, i
- warehouse capacity — the amount of storage space in a warehouse
- western isles pony — a breed of large pony, typically grey, with a dense waterproof coat. The only surviving variety is the Eriskay pony
- white iron pyrites — marcasite
- white-spotted hyla — a type of tree frog (H. leucophyllata) of tropical America
- wild passionflower — the maypop, Passiflora incarnata.
- wilson's phalarope — a phalarope, Phalaropus tricolor, that breeds in the prairie regions of North America and winters in Argentina and Chile.
- wireless telephone — Now Rare. radiotelephony.
- wireless telephony — Now Rare. radiotelephony.
- withdrawal symptom — effects of stopping a drug
- women at point sur — a narrative poem (1927) by Robinson Jeffers.
- working hypothesis — See under hypothesis (def 1).
- world championship — an international competition in a particular sport or activity for people all around the world