1 a : to look at someone or something secretly especially from a hidden place
A little girl peeked around the corner of the chair at him.
She peeked [=peered] through a hole in the fence.
Close your eyes, and no peeking!
b : to look at something briefly
She peeked ahead to the next chapter to see what happened next.
He allowed some of his friends to peek at his next painting.
2 : to show slightly : to be slightly visible — usually + out
Her slip peeked out from beneath her skirt. [=a small part of her slip could be seen beneath her skirt]