To feel dull, or an ache, heavy, tight or otherwise unwell in your heart. Occurs when someone you love is far away, or you've done something to hurt them and you don't know how you'll fix it, or when fate conspires to keep you apart, or in any less serious but just as pathetically painful situation.
Girl: Hannah's been away for two weeks already. Getting her post-card just made me feel so...

Friend: Heartsick.

Girl: Yeah. Heartsick.
by Lex Lemon December 11, 2010
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Heartsick works when you're all mopey &"Mehh I miss him" but you're most definitely nothing remotely broaching anything near 'in love' cos that's just ridiculous cos you're 15 and far too young to be in love with anyone but Mark Owen (cos he's adorable and would never break your heart ((and also blatantly gay)) ), and also because just no, love doesn't happen to down-to-earth girls like you.
"Aw, you're lovesick."
"What's another word for love?"
"Heart, why?"
"I'm heartsick. Love is too strong a word."
by AntiRomanticism December 5, 2006
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Heartsick is when you're all mopey and "Mehh I miss him," but you're most definitely, nothing remotely broaching, anything near 'in love', 'cos that's just ridiculous, 'cos you're 15 and far too young to be in love with anyone but Mark Owen ('cos he's adorable and would never break your heart ((and also blatantly gay)) ), and also because just no, love doesn't happen to down-to-earth girls like you.
Girl: "Mum, what's a word for 'lovesick', that isn't 'LOVEsick'?"

Mum: "Uhm.. 'heartsick'?... Why?"

Girl: "'Cos 'love' is a big, scary word Mum!"
by Luciole December 3, 2006
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