A board foot is one foot long, one foot wide and one inch in thickness. Checking the Waste Mary Huston Gregory This is usually expressed in pounds per thousand board feet, a board foot being considered as one-twelfth of a cubic foot.
Sibilance is a manner of articulation of fricative and affricate consonants, made by directing a stream of air with the tongue towards the sharp edge of the teeth, which are held close together; a consonant that uses sibilance may be called a sibilant, or a strident.
A sill is an intrusive rock formation. These formations occur when magma solidifies underground and then intrudes into the overlying rock formation. They are distinct from similarly formed domes and dikes because sills are horizontal to the surface.