막중해요 · 막중했어요 · 막중한 (+noun)
very important, weighty, grave (responsibility, duty)
Example
팀의 대표로서 제 책임이 막중합니다.
As the team's representative, my responsibility is very heavy.
Word parts
막 nothing+중 heavy
Literally 'nothing heavier'.
Good to know
Pairs with 책임 or 임무: 막중한 책임 'a heavy responsibility'.