IPA: /ˈʌndərʃrʌb/
KK: /ˈʌndərˌʃrʌb/
A type of small bush that grows close to the ground.
The garden was filled with colorful flowers and low undershrubs.
Undershrub is formed from "under" (from Old English "under", meaning beneath or below) and "shrub" (from Old English "scrybb", meaning a woody plant). The word refers to a woody plant that grows beneath taller vegetation.
Think of a plant that grows 'beneath' ('under') taller plants, which is what an undershrub is.
No commonly confused words.