As a Noun: 1. One of the sixty parts that a minute is divided into. English = second. 2. A very brief period of time. English = second. Informal English = sec. 3. In mathematics, the ratio of the hypotenuse to the shorter side adjacent to an acute angle (in a right angled triangle); the reciprocal of a cosine. English = secant. 4. In geometry, a straight line that cuts a curve in two or more parts. English = secant.