means To take a quick or sneaky look at something, often through a small opening or before you're supposed to.

from From Middle English piken (also spelled peken), meaning to look quickly or peer. Its early life is tangled with peek's near-twin peep, and the two have long traded glances and spellings; the deeper root before Middle English is uncertain. It also sits in a family of words like peer and pry, all describing the same furtive lean toward something half-hidden.