watered stock Stock sold for a price below its par value.

weak efficiency A market has weak efficiency if prices fully reflect any information contained in past price data.

when-issued security A government security that trades forward in advance of being issued.

white noise A simple form of stochastic process.

Wiener, Norbert Mathematician who proved the existence of Brownian motion.

Wiener process Brownian motion.

Working, Holbrook Early researcher of the random walk hypothesis.

WorldCom bankruptcy The largest bankruptcy in US history.

worst-of option A form of rainbow option.

wrangle An options spread that is long (short) both a ratio call spread and a ratio put spread.

writer extendible option An option whose expiration is extended if some pre-defined condition is met.