A common phrase used to refer to someone who's perception is very, very slow. An imbacil
for example. Someone who just can't understand.
A: Excuse me, what time is it?
B: Time for you to go home and play with soap!
A: But my mom will be angry if I waste soap?!
B: The light is on but nobody is home
The raw definition in hebrew means Rabies, a fatal disease associated usually with canines, but can inflict other animals and even mankind. The less formal use is to describe anything that isn't good. And that includes anything.
A: Do you see this ugly girl?
B: yes, kalevet
A: how was the test?
B: kalevet, I knew nothing
A: I heard about youe rash
B: It's a kalevet of eczema