(sports) A rule in some sports that allows players to enter and leave the game for other players many times during the course of the game, and for coaches to bring in and take out players an unlimited number of times.

plural of substantive case

A family of technologies that provides digital data transmission over the wires of a local telephone network. Often, this notion is used for the Asymmetric Digital Subscriber Line (ADSL), the most commonly installed technical variety of DSL.

plural of subspecific name

(rugby) A temporary substitution for a visibly-bleeding player who must leave the field of play for first-aid treatment.

(lexicography and grammar) Abbreviation of substantive.

plural of substitution cipher

plural of subspecific epithet

(theology) The theory of atonement which holds that Jesus died on the Cross in place of human sinners.

(anatomy) Situated under, or on the ventral side of, the sacrum.