Definitions

1. noun

a muscle that contracts to cause hair or other structures to stand on end, especially the arrector pili muscle that stands the hairs of the skin upright.

“The arrector muscles in his arms contracted, causing the hairs to stand on end.”

2. noun

a muscle that adjusts the position of a body part, especially in invertebrates.

“The arrector muscles in the squid’s body helped it change direction quickly.”