have a cow

have a cow {very informal} (to become very angry or anxious about sth; become angered, get angry, become mad; overreact;to get all worked up about the news that is shared; to become amazed, angered, or upset) — беситься, злиться, разозлиться, разъяриться, впасть в ярость; ~ писать кипятком, ~ ссать кипятком

Буквально это переводится как «рожать корову» и обычно означает «неадекватно реагировать на плохие новости», т.е. «чрезмерно выходить из себя».
We use the idiom "have a cow" to describe someone's reaction to something that happened:
......She had a cow when I said I wasn't going to the picnic.
Sometimes the expression is used in anticipation of an emotional response. One might say

.....The boss will have a cow when he learns what the new employee did to the company car.
..... A parent might have such a reaction (have a cow) if a child fails to meet an assigned curfew.
..... The record companies were having a cow over downloadable music files. (thefreedictionary.com)
Or to tell someone not to react so strongly:
..... Don't have a cow just because I'm not going to the picnic.

...... My mom had a cow when ...
(=My mom was freaking out and upset when...)
............. I told her I wrecked the car.
............. she saw how messy the kitchen was/she saw the mess we made.
............. she saw me smoking/ found out I was smoking
............. my teacher called them and told her/them about my poor grades
(=My mom was freaking out and upset.)
My mom / parents/etc
... nearly killed me when...
... threw a fit when...
... really got on my case when...
... went ballistic when...
... went postal when...
(to go postal is chiefly North American slang, meaning "to suddenly behave in a very violent or angry way")
... was really pissed when...
... got so pissed off when she found out I was smoking."
(I'd never smoke in front of my mom. I don't want to piss her off.)
... blew a gasket...
... flipped (her lid)...
... chewed me out...

These mean she was very angry. If you want to emphasize how she expressed this anger, I'd say she:

... screamed at me
... bitched at me
... tore my head off
... ripped me a new one (meaning "ripped a new asshole in me")

... freaked out
... flipped out
... lost her mind
Usage notes: the opposite meaning is expressed by don't have a cow

Usage note:
This is not the usual have as "to own a cow". It is the action verb have as in "to give birth to a cow". In other words, we don't say "the record companies *had a cow" but "the record companies were having a cow". They were upset, as if experiencing a very unpleasant ordeal.
Expanding on this a bit:
If you (men, use your imagination) understand that giving birth to a child is a trying (and painful) experience, then imagine what it would be to give birth to a cow. So, "don't have a cow", would express the notion that you should not experience something well out of the norm of pain and suffering. Basically--relax, it won't be that bad.

- I just wanted to point out that "have a cow" sounds very dated to my ears. It was something we said every other minute about 10 years ago, but I can't imagine anyone saying it seriously now. I haven't heard any younger speakers use it either, so I think it's one of those poor expressions of the 90's that went the way of "dude." (wordreference.com)
- It is a dated saying, it was given promises in the 90's with “The Simpsons” as it was a well know catch-phrase of Bart Simpson. “Don’t have a cow man!” (wordreference.com)
- I teach and coach high school students. Have a cow is not in current use, although dude still seems to be popular.(wordreference.com)
There are lots of expressions that mean to get/become/ upset or angry. I had never heard this one and, from the comments above, it is out of date now.

Alludes to the state cows are in before delivery.
The expression "have a cow" is said to have originated in the 1950s, although an earlier British expression, having kittens"," did cover the same territory. The idea is that certain bits of unexpected or bad news might create the same agony and pain as literally giving birth to a cow. There is every chance that the recipient of bad news might react badly, going ballistic or blowing his or her top.


What is the meaning of "have

What is the meaning of "have a cow"?

... This informal expression is used quite often by Homer and the members of his family. When you tell someone "don't have a cow" what you are asking them to do is to calm down. You are telling them not to get excited. Here are a few examples.

..... Anand had a cow because his daughter got her hair cut really short.
..... My boss was having a cow because the project was getting delayed.
..... Come on Sachi, don't have a cow!