Altamira Airport (IATA airport code "ATM"), an airport in Brazil

Air Traffic Management

Automated teller machine, a cash dispenser or cash machine

Asynchronous Transfer Mode, a telecommunications protocol used in networking

"Able Toastmaster", used as a postnominal for people granted awards from Toastmasters International

Amateur telescope maker, a person who makes telescopes as a hobby

Active Traffic Management, a motorway scheme on the M42 in England

Awareness Through Movement, a group lesson in the Feldenkrais method

Aggregate Trailer Mass, the total mass of a fully laden trailer

ATM Gateway, Athlone, Tullamore, Mullingar Gateway or Midlands Gateway

Adobe Type Manager, typeface management software from Adobe Systems

At-the-money, a term used in option pricing

Ataxia telangiectasia mutated, a protein kinase that plays a role in response to DNA damage

Atmosphere (unit) ("atm"), a unit of atmospheric pressure

Ass to mouth, a sexual act in which participants go directly from anal sex to fellatio

Association of Teachers of Mathematics, a UK teacher organisation

In Finnish, alempitasoinen mies, a "man of inferiour value". This Finnish WWW slang abbreviation refers to a man afflicted with the so-called Nice Guy Syndrome.

Actun Tunichil Muknal, cave in Belize of interest in Mayan archaeology

Automatenmarken, (German) a gummed or self adhesive label for postal use

Azhagiya Tamil Magan, a Tamil film starring Vijay and Shriya Saran released in 2007.

Andrew "Test" Martin, a retired Canadian professional wrestler