An abbreviation of the words 'Aliens Made Them Do It'. Used in FanFic it is a term used to describe a story in which aliens somehow encourage or force the pairing of the story to have sex.
It is also used to lessen, justify or explain a NonCon or Dubious Consent warning.
It is used primarily in Science Fiction related FanFic such as SGA and StarTrek Fandoms. It is often a parody or Cliche fic.
1) This story is an AMTDI, McShep, where aliens give them aphrodisiacs.
2) This story is an AMTDI NonCon where aliens force Rodney and Teyla to have sex together.