| Main Entry: | intrusive rock |
| Part of Speech: | n |
| Definition: | in geology, magma forced into cavities or cracks of other rocks and crystallized but not reaching the surface; also called plutonic rock, igneous intrusive rock |
| Example: | In composition, intrusive rocks include the entire sequence of igneous rock types from the dense and dark ultramafic peridotites to the very light-colored and low-density alkali granites and syenites. |
| Etymology: | 1844 |