Initialism of sewage treatment plant. / (physics, chemistry) Initialism of standard temperature and pressure. / (networking) Initialism of spanning tree protocol.

(construction) Initialism of subject to planning.

plural of STP

(travel, aviation) Initialism of stopover paid by carrier. Pre-arranged hotel transit accommodation, paid by an airline to encourage use of a bad connection on their services.

Initialism of schizotypal personality disorder.

Alternative form of StPD