gray matter

gray-matter的词性：
n.（名词）

1. Brownish-gray nerve tissue, especially of the brain and spinal cord, composed of nerve cell bodies and their dendrites and some supportive tissue.
灰质：浅棕灰色的神经组织，尤指脑和脊髓的灰质， 由神经细胞和其树突及一些相关支持组织组成

2. Informal Brains; intellect.
【非正式用语】 脑；智力，思维能力