I. “+ adjective
Etymology: semi- + automatic
: not fully automatic: as
a. : operated partly automatically and partly by hand
a lathe that operates automatically after insertion of the rough piece by the operator is semiautomatic
b. of a firearm : that employs gas pressure or force of recoil and mechanical spring action in ejecting the empty cartridge case after the first shot and in loading the next cartridge from the magazine but that requires release and another pressure of the trigger for firing each successive shot — compare automatic 5
• semi·automatically “+ adverb
II. noun
: a semiautomatic device or machine ; especially : a semiautomatic firearm