COMINT - "communications intelligence" i.e. technical data and intelligence derived from foreign communications by other than the intended recipients.
ELINT - "electronic intelligence" i.e. intelligence and technical data gleaned from electronic transmissions such as email, text messages, Internet traffic, or electronic transmissions of any kind.
ECHELON - Designed and co-ordinated by NSA, the ECHELON system is used to intercept ordinary e-mail, fax, telex, and telephone communications carried over the world's telecommunications networks. Unlike many of the electronic spy systems developed during the Cold War, ECHELON is designed primarily for non-military targets: governments, organisations, businesses, and individuals in virtually every country. It potentially affects every person communicating between (and sometimes within) countries anywhere in the world.
HUMINT - "human intel" i.e. intelligence (information) gathered the old fashioned way by talking to people, as opposed to obtained via technology. The secondary recurring character of Seymour Lafortunata is the NSA humint expert shown on the series.
JMD - "Jake Monitoring Device" hand-held PDA which Dr. Diane Hughes uses to monitor Jake's vitals and nanite activity. Its screen has been known to freeze (Last Man Standing).
Sat Ops - Satellite Operations. The control room located in the Operations Building at NSA Headquarters in Fort Meade, Maryland where Lou and Kyle work with dozens on Intercept Operators, monitoring global communications and missions.
SIGINT - "Signals Intelligence" i.e. intel gathered from radio, radar, and other transmissions
medlab - Diane's "home base" where she and Fran work.