To be on one's guard or raise one's defenses; to react with fear, suspicion, or distance. (verb)
Examples of word bristle
The Major looked at the Texans with cold contempt—the tone of his voice alone made Call bristle.
Awned having an _awn_, that is, a bristle-like appendage, especially on the glumes of grasses.
Sporangia clustered around the slender bristle, which is the prolongation of a vein, and surrounded by a vase-like, slightly two-lipped involucre.
The most characteristic feature is the long caudal bristle, which is extremely delicate and about two-thirds the length of the body.
It is also called bristle-tail, because of the long, bristle-like parts at the end of its body; and in some places it is called a slink, because, you know, it loves dark places, and when you uncover it in the daytime, it slips around a corner into the dark again.
Amélie, shows a mere fringe of dark bristle, which is tree, based upon a broad red-yellow streak, which is land.
Reid and Polosi now occupy the high ground and Bush has only just begun to 'bristle'.
Herman's "bristle" has nothing to do with what I think.
Paula Dobriansky is too much the diplomat to ever "bristle" at a question.