In
geology, a
sill is a tabular mass of
igneous rock that has been intruded laterally between layers of
sedimentary rock, beds of
volcanic lava or
ejectmenta[?], or even along the direction of the
foliation[?] in
metamorphic rock. The term "sill" is synonymous with "intrusive sheet."
In architecture, the sill is the bottom edge of a window.