The normal abbreviation of American Express. For Voice Auth call 800-528-2121, for Customer Service call 800-528-0682, for merchants that want to accept Amex call 800-528-5200.
Abbreviation for Australian Monsoon Experiment, a program of enhanced upper-air soundings and radar data collection in northern Australia aimed at better documentation of those large-scale weather patterns over Australia that are associated with the ebb and flow of the Australian monsoon. See Holland et al. (1986).
Abbreviation for American Express, an organization that issues travel and entertainment cards and acquires transactions.