U.L. - Underwriters Laboratory. An organization which grants electrical ratings.

U.S.S.G. - U.S. Standard Gauge.

U/W - Underwriter.

Union - An organization of workers formed with the purpose of protecting workers' rights and increasing bargaining power with an employer on such issues as wages, hours, and benefits.

Union Steward - An on-site union official elected by coworkers to oversee a particular union's work in a facility and resolve any disputes over union jurisdiction. Also known as Shop Steward.