IPA: /ˈʌndərˌmoʊst/
KK: /ʌndərˈmoʊst/
The word describes something that is at the lowest level or position, often referring to the bottom layer or part of something.
The undermost layer of the cake was made of chocolate.
In or to the lowest position or level.
The treasure was hidden in the undermost layer of the sand.
Undermost → It is formed from "under-" (meaning beneath) and "most" (meaning the greatest or highest degree). The word "undermost" refers to the lowest or deepest position, being beneath everything else.
Think of something that is 'beneath' ('under-') and at the 'greatest degree' ('most') — that's why undermost means the lowest or deepest position.