1.
central pillar of a traditional Japanese house
The main structural pillar in a traditional Japanese building, typically the thickest and strongest column supporting the entire structure.
2.
breadwinner; mainstay; key person
Figuratively, the person who is the main support of a family, organization, or team. The one everyone depends on.
Named after 大黒天 (Daikokuten), the god of wealth and prosperity. In traditional Japanese houses, the 大黒柱 was positioned near the center of the home and was both structurally and symbolically important. The figurative sense (breadwinner, mainstay) is more common in everyday conversation. Collocations: 家族の大黒柱 (family breadwinner), チームの大黒柱 (team's key player), 大黒柱を失う (to lose one's mainstay).