Same definition for 'lol' (see 'lol' if u don't get it). Except in 'Trololol' it's almost like triple lol. Therefore maximizing the effect of the 'lol' in a particular situation. Note: no set number of lols at the end of 'tro' e.g trololol and trolololololol - number of lols at the end just maximises 'lol' effect.
Dan: Oh shit! I just sharted (accidentally shitting when farting)