(1) A term used to indicate the density of ends or picks or both in a woven fabric, usually expressed as the number of threads per centimetre. The state of the fabric at the time should be described e.g. loomstate or finished.
(2) Synonym for count of reed.
(3) The term may be used in such phrases as high sett, closely sett etc., where a high end or pick density is indicated.
Textile Resource (http://www.textile.org.uk)