prep

• Indicating time of occurrence, especially an instant of time, or a period of time relatively short in context or from the speaker’s perspective.
  "balance as at 20th March 1999"
• (used for skills (including in activities) or areas of knowledge) On the subject of; regarding.
  "The twins were both bad at chemistry."
• (Ireland, stressed pronunciation) Bothering, irritating, causing discomfort to
  "I think ‘Jesus, my back is at me’. Then I get the ball. Off you go for 10 yards and you don’t feel a thing. Then you stop and think: ‘Jesus, it’s at me again’[.]"

verb

• (informal, neologism) Rare form of @; to reply to or talk to someone, either online or face-to-face. (from the practice of targeting a message or reply to someone online by writing @name)
  "If you have questions or observations on my discussion questions, feel free to reply to this email, at me on Twitter, or comment on the companion post on AMV."

pron

• (Northern England, rare, possibly obsolete) Alternative form of 'at (relative pronoun; reduced form of “that” and/or “what”).
  "Tak us t’ foxes, t’ little foxes at spoils t’ veynes: fer our veynes hev tender grapes."

noun

• (software) Initialism of assistive technology.
• (US, Navy) Initialism of auxiliary tugboat.
• (US, sports) Initialism of anaerobic threshold.
• (fan fiction) Initialism of alternate timeline.