Being lovesick is when youlove someone so much that you can't function normally. You get nauseous, stomachaches, and you cant eat. When I get lovesick I cant eat for days and my stomach is always in knots.
Nial was lovesick. He couldn't take a bite of food without feeling like he needed to throw up. All he kept thinking about was her..
A deep, often depressing, feeling of wanting to find love; to be loning for love; to be without a companion to share ones life with, though it is desired deeply.
(Don't believe the other definition that has all those thumbs up for saying it is being in love and "drawing hearts in the sand" and stuff, becauase that is the opposite, that is lovestruck, not lovesick).