This can be an insult, an expression of pity/sympathy, or even a compliment, depending on the context. As an insult, it can mean a variety of things, ranging from "what an idiot" to "f*** you". In a more sympathetic way, it can mean something to the effect of "I feel bad for you/so-and-so" or "what a shame". As a compliment, it can actually mean "what a sweetheart" or "how cute/sweet". In that sense, it's typically referring to someone's innocence or as a term of endearment.
Examples of "bless your/his/her/their (little) heart(s)" in typical conversation:

Insult (what an idiot):
"His boss told him if he made another careless mistake when filing the data reports again, he'd fire him on the spot. Bless his heart."

Insult (f*** you):
"Hey baby, you've got to be the sexiest little thing here. How about you and I head back to my place and throw our own private party?"
"Bless your little heart. Thanks, but I think I'll pass."

Pity/Sympathy (I feel bad for you/so-and-so):
"Bless her heart, she worked so hard to bake a nice cake for her mom's birthday. But she tripped while carrying it and it was ruined when it fell on the ground."

Pity/Sympathy (what a shame):
"He could have been top of his class, if he hadn't started started skipping class to hang out with those troublemakers. Bless his heart."

Compliment (what a sweetheart):
"I don't know how she finds the time to raise those kids, clean her house, work as a part time substitute teacher, volunteer for church events, and still host occasional social gatherings in her home. Bless her heart, she's a saint!"

Compliment (how cute/sweet):
"Look, mommy! We made macaroni art at school today! Do you like it? I made it just for you."
"Bless your heart, you're so thoughtful. I love it! We'll put this on the fridge for everyone to see!"
by TygraSol February 03, 2018
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3:45...I think? Who knows what this means really?
What time is it? Half past a monkey's ass, quarter to his balls.
by HK Orlando October 19, 2006
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When someone behaves in a way so as to think that you are stupid, when really you are the one playing them.
When the little man drank the poisoned wine in "Princess Bride," Wesley sucked his man boobs clean of fat and milk.
by SoftCrumb October 14, 2021
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When bro is meat riding somebody it also means zip up his paints when you done sucking his dick
Person 1 Bro kd is better than mj

Person 2 Zip up his pants when you done
by Zip up my pants bitch April 22, 2023
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To throw up; to vomit.
I had a few too many wobbley pops last night and I spent all morning saying hi to Ralph on the big white telephone.
by northerner1 September 25, 2007
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a term often used by primary school students which is the equivalent of who farted?
*strage smell in the air*
Lil Timmy: AWW! FESTY! who let fluffy off his chain!?!
Bobby: It wasn't me *picks nose*
by salmon_attack May 23, 2005
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