submillimeter

adjective
sub·​mil·​li·​me·​ter | \ ˌsəb-ˈmi-lə-ˌmē-tər How to pronounce submillimeter (audio) \

Definition of submillimeter

: being less than a millimeter in diameter or wavelength a submillimeter particle a submillimeter radio wave

First Known Use of submillimeter

1954, in the meaning defined above

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