Have a cow, Don’t have a cow, or I almost had a cow are informal ways of saying you were very close to becoming angry, upset, or agitated. It’s similar to saying, “I almost lost my temper,” or “I almost threw a fit.” 

• “Have a cow”: This slang phrase means to become extremely angry or upset. 
• “I almost had a cow” implies that you were on the verge of becoming very angry, but you managed to control yourself. It’s a way of expressing that you were close to losing your composure. 
• “Don’t have a cow” suggests you shouldn’t get mad at something or someone.

For example: “I almost had a cow when I realized I forgot my wallet,” meaning you were close to getting very angry and upset about forgetting your wallet. 

If I tell my wife where I’ve been, she’ll have a cow.

Don’t have a cow—it’s no big deal.

My teacher had a cow when she realized nobody had done the homework.

The workers complained to their boss because the manager always had a cow over unimportant things.

Tradução: ter um ataque, chilique, um surto, ter um troço.