An investor who deals in securities only occasionally, especially when he/she deals only in small quantities. Odd-lotters are also called (more formally) small investors. Odd-lot theory holds that odd-lotters are both poorly informed and risk averse; this theory encourages larger investors to do the opposite of whatever odd-lotters tend to be doing at a given time. This theory has little evidence to support it, and few have held it since the 1990s.
An investor who buys and sells securities in less than the standard unit of trading. Odd-lotters are generally small investors lacking the financial resources to engage in larger trades.