letter security

A security that is not registered with the SEC, and so cannot be sold publicly in the marketplace.

Investopedia Says:
The name comes from the SEC requirement for an "investment letter" from the purchaser, stating that the purchase is for investment purposes and is not intended for resale.

Also known as letter stock or letter bond.

Stock or bond that is not registered with the Securities and Exchange Commission and therefore cannot be sold in the public market. When an issue is sold directly by the issuer to the investor, registration with the SEC can be avoided if a Letter of Intent, called an Investment Letter is signed by the purchaser establishing that the securities are being bought for investment and not for resale. The letter's integral association with the security gives rise to the terms letter security, letter stock, and letter bond. Also called 144 stock and controlled and restricted stock. See also Securities And Exchange Commission Rules; Restricted Securities.

Category of stock that derives its name from an inscription on the face of the Stock Certificate, indicating that the shares have not been registered with the Securities and Exchange Commission and, therefore, cannot be sold to the general public.

The noun has one meaning:

Meaning #1: a stock or bond that is not registered with the Securities Exchange Commission and cannot be sold in the public market