(1) Abbreviation of "standard." For example, designations for Internet protocol standards originally used an STD number. STD was later replaced with Request for Comment numbers (see
RFC).
(2) (
Subscriber
Trunk
Dialing) Long distance dialing outside of the U.S. that does not require operator intervention. STD prefix codes are required and billing is based on call units, which are a fixed amount of money in the currency of that country. For example, one call unit may be charged for establishing the call, and each call unit pays for some amount of time depending on the distance between parties.