An intrusive igneous rock body that is tabular and concordant is called a sill.

Here's a breakdown of the terms:

* Intrusive: The rock formed from magma that cooled and solidified beneath the Earth's surface.

* Tabular: The rock body has a flat, sheet-like shape.

* Concordant: The rock body is parallel to the layering (strata) of the surrounding existing rock.

In simpler terms: A sill is like a flat pancake of igneous rock that has been injected between existing layers of rock.