noun

• (US, mainly 1920–1930) A transient worker who would move from boom town to boom town in search of temporary work.
• (US, nautical, military, slang) A nuclear ballistic missile submarine, SSBN.
  "Distant contact, probably submerged. It's a wild guess, but I'd say we hit a boomer coming out of the barn. Could be a missile boat out of Polijarny."
• (UK) A Eurasian bittern (subfamily Botaurinae).
• (Appalachia) A red squirrel (Tamiasciurus hudsonicus).

noun

• (informal) Ellipsis of baby boomer.
  "Boomers came of age in the era of the Beatles and Led Zeppelin."
• (by extension, slang, sometimes derogatory) An elderly person, regardless of generation.
  "I'm going to be a boomer by the time this thing is over."
• (by extension, slang, sometimes derogatory) A person who is too old to be familiar with the use of recent technology.
  "I'm such a boomer; I have no idea how to use this phone."

noun

• (US, historical) A member of a 19th century movement which campaigned for the opening of "Unassigned Lands" within the Indian Territory (now Oklahoma) for settlement.
  "Some skunk of a Sooner, sneaking in ahead of the Run, had set the blaze to keep the Boomers off, saving the land for himself."