Real Dictionary

peak in American English 1
a tapering part that projects; pointed end or top, as of a cap, roof, etc.
adjective: being at the point of maximum frequency, intensity, use, etc.; busiest or most active
intransitive verb: to project in a peak
noun: the pointed top of a mountain or ridge
transitive verb: to raise the after end of (a yard, gaff, etc.) to or toward an angle above the horizontal

peak in American English 2
to become sickly; waste away; droop
intransitive verb: to become weak, thin, and sickly

peak in British English
adjective: of or relating to a period of highest use or demand, as for watching television, commuting, etc
noun: a pointed end, edge, or projection
verb: to set (a gaff) or tilt (oars) vertically

peak in Electrical Engineering
adjective: The peak value is the maximum value of an alternating or other waveform.