zhǔ​gàn

core

主干 (主幹) zhǔ​gàn
core noun
the most important or fundamental part of a system, organization, or structure

These experienced engineers are the technical backbone of the entire project.

trunk noun
the main stem of a tree or plant, as distinct from the branches and roots

The main trunk of this ancient pine is very thick, requiring two people to encircle it.

Frequency

Movie subtitles
0.060 per million appears in 0% of films
Written text
3.40 per million

Sources

Definitions
CC-CEDICT