Abreviation of 'good times.' Singallying a fun event or passage of time. Used specifically to refer to a memory or referance something that was a 'good time.'
Man, remember when we robbed that bank, went to vegas, doubled up and bought all that blow? that was gt's.
GT's are all round Good Times, generally shared at preambles and other such drinking events. implies enjoyment by all parties involved. Often the result of jesting behaviour
funelling post exams, sharing jesting moments with mates would both be classified as GT's. if two friends were to be involved in a physical alteration it would not be good times.