What does "trivial" mean in logic? 
An argument that contains contradictory premises is trivial in the sense that there is a valid argument from the premises to any well-formed formula whatsoever.

Is the statement true or false? I can't understand what it means for an argument to be 'trivial'.

True. In logic, 'trivial' is a technical term. A trivial theory is such that it has all the sentences as theorems. This is possible only if it contains an inconsistency, which enables one to derive any sentence at will.
So, why do we bother with such a term? Because we can have rational systems that have inconsistencies, but the associated theories are non-trivial. Paraconsistent logic studies such systems.
