Heavier means greater in weight. Heavier than air, heavier than expected, get heavier.
It is the comparative of heavy and takes than. Heavier-than-air flight is the fixed technical phrase distinguishing aeroplanes from balloons. Heavier also covers rain, traffic and workload — heavier rain, heavier traffic. Note that heavy has many senses and heavier follows them all: a heavier sentence, a heavier accent, heavier going.
1adjectiveheavierGreater in weight.
“This suitcase is much heavier than mine; what have you got in it?”
heavier is a comparative of weight.