1) Reaching a high 2) Reaching a high point 3) Ruler in a vegetable garden 
• (p. pr. & vb. n.) of Peak • (a.) Pining; sickly; peakish. • (a.) Mean; sneaking.
Peak'ing adjective 1. Mean; sneaking. [ Vulgar] 2. Pining; sickly; peakish. [ Colloq.]
This is the response curve of an equaliser unit that affects a selected band of frequencies. For example: a bandpass frequency response.
A seam that is peaking is one that is generally higher than the other areas of the carpet. Most often this is due to improper carpet installation. It is also caused by the carpet installer running the padding seams in the same direction as the carpet seams (normally, this should not be done).