This phrase usually means "that's sexy" although it can also mean "that's cool."
In 2005, celebrity Paris Hilton began using "that's hot" as a catch phrase, increasing the popularity of the less common "that's cool" meaning.
The more traditional "sexy" meaning:
Chad: Check out my new miniskirt.
Derek: That's hot!
The recently popularized meaning:
Chad: Check out the celebrity phone numbers I downloaded from some the net. Some stupid famous chick had them on her mobile phone and they got stolen.
Paris: That's hot!
Phrase made famous by wold-renowned genius Paris Hilton. Sounds like the opposite of "That's cool" but means the same thing.
(Blasts Paris Hilton between the eyes with double-barrel shotgun)
"Now THAT'S hot, skank."
A phrased used since forever recently trademarked by Le Paris Hilton. It can be used in whatever situation, and it will always make sense.
Your grandma died.
Can you take out the garbage?
It lightens up the situation.
A phrase made popular by Paris Hilton.
The phrase is used after basically any statement.
Used in everyday speech.
Jason: Look at those two chicks making out
Ryan: That's hot
Roxy: Like my new Gucci shades?
Lauren: That's hot
Random guy: I robbed a bank
Paris Hilton: That's hot
Expression Popularized by Paris Hilton. Frequntly used by hipsters who should know better but are desperate to sound cool and cutting edge hip.
Adam: What do you think about this?
Levi: That's Hot.
Adam: What did you just say?
Levi: That's hot.
Levi: What was that for? That fucking hurt.
Adam: Eye gouging it the suitable punishment for saying "That's Hot".
You said it twice, therefore you are blind. Say it again and I get to kick you in the nads until you can't breathe. SAY IT AGAIN!!
Made popular by Paris Hilton meaning "That's cool" "That's awesome" "That's nice" etc.
"Her cell phone has diamonds all over it! That's hot"
It should be noted that Paris Hilton did not actually orginate the term, That's Hot. It was used in black urban areas before it became mainstream. As different cultures interact more and more, and with the prevelence of Hip-Hop, it can be easily seen (via celebrity photos and other media) that the likes of Paris Hilton are hobnobbing with those of Damon Dash and Jay-Z - hence, the possibility and probability of such slang rubbing off on Hilton. As she is in continuous spotlight with (suspected) limited vocabulary abilities, it makes sense that she would be assumed to have originated it, as it is all she seems to utter. But she is not original.
Yo, son, that's hot.
"See that new Monte Carlo, that's hot and on fire.." #1 Stunnas, -Big Timers, f/ Lil' Wayne, Juvenile
"This is Why I'm Hot.." - Mims