This is the 12935th most frequent Spanish word.
pegar
"To hit, stick, glue, or attach."
In this sentence, 'pegar' is used to mean 'to stick' or 'to adhere' one object to another.
Voy a pegar el papel en la pared.
I am going to stick the paper to the wall.
Here, 'pegar' is used idiomatically in the phrase 'pegar un grito,' meaning 'to shout' or 'to let out a cry'.
Pegó el grito cuando vio la araña.
They shouted loudly when they saw the spider.
In this context, 'pegar' is used reflexively, 'pegarse,' to mean 'to hit oneself with something.'