knurl

Short definition from Wiktionary

Noun

1. 1
   A contorted knot in wood.
2. 2
   A crossgrained protuberance; a nodule; a boss or projection.
3. 3
   A lined or crossgrained pattern of ridges or indentations rolled or pressed into a part for grip.

Verb

1. 1
   To roll or press a pattern of ridges or indentations into a part for grip.