submillimeter

[ suhb-mil-uh-mee-ter ]
/ sʌbˈmɪl əˌmi tər /

adjective

less than a millimeter in size: a submillimeter wave.

Origin of submillimeter

First recorded in 1950–55; sub- + millimeter
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019