Also found in: Dictionary, Thesaurus.
Related to letter security: letter stock
A stock or right that one acquires through some means other than the open market. One may receive a restricted security through a merger or acquisition, private placement prior to an IPO, or sometimes through a stock option. A restricted security is not registered with the SEC and thus may not be sold publicly until registration has been made. It is less commonly called a letter security.
See restricted security.