The word "contract" is referring to a muscle doing work, and the opposite is relax. Skeletal muscles work in pairs, and often one of the pair will contract while the other relaxes.
Contract or shrink.
mountainous
Powerful.
Actually, the word would be nerdy.
Profit
contract
contrary contradict
Maybe outgoing, which means friendly or sociable.
The opposite of hit is miss.
contract, decrease, diminish.
ept - If inept means incompetent, then ept, as its opposite, means competent and therefore expert.
A four letter word that is opposite of received and starts with the letter g is gave.