Definitions for "Intrusive rock"
Igneous rock that is interpreted as a former intrusion from its cross-cutting contacts, chilled margins, or other field relations.
Igneous rock that, while it was fluid, penetrated into or between other rocks and solidified. It can later be exposed at Earth's surface after erosion of the overlying rock.
It is an igneous rock which has been formed underground from magma being stuffed into the cracks.