Peek is a verb that means to take a quick, secretive or furtive look. If you want to use an alternative to peek, there are several synonyms to choose from. One such synonym is glance, which refers to a brief look that is directed towards something. Another word that closely related to peek is glimpse and it suggests a fleeting look or short view. If you want a more casual and spontaneous alternative to peek, then you may consider using the word check. Lastly, if you want to imply that the look was done in a very discreet manner, use the word spy.