No, It doesn't mean sustain. Sus is short for "suspended". all the names for chords are descriptive, meaning that you can derive the spelling of a chord from the name. The simplest description of suspending a chord is to replace the 3rd degree of a chord with the 4th degree. So if you are for instance playing a CMajor triad you have C,E and G as 1.3 and 5 if you replace the E with an F (raise the 3rd a half step) you have a suspended C or a C sus.

Sus chords are especially usual in pop music. Sus is an abbreviation of ´suspended ´. In a theoretical feature what’s happening with the chord when you add sus to it are that the third note in the scale is flattened or raised one step. There are sus2 and sus4 chords. In the first case, the note is demolish and in the second case it’s raised.