(noun) a large/thick/chunky/big girl/fat chick/BBW. Because she doesn't have the same good looks as a skinny girl, she puts in more effort to get the interest of guys by being nicer to them. A tries-harder will often buy guys drinks, make them food and give incredible blow jobs.
Dude that big girl over there is a total tries-harder. Nathan hit it last weekend and after she gave him incredible head she actually made him a sandwich!