Physical or metaphorical support: a pole, strut, or person/thing that holds something up or serves as a mainstay.
I set up a support pole for the tomato seedling.
We drove props into the ground to set up the tent.
彼はチームの精神的な支柱だ。
He is the emotional pillar of the team.
He became the mainstay of the team.
I secured the support pole in preparation for strong wind.
柱 is a general architectural pillar or column, while 支柱 is specifically a prop or brace added for support, often temporary or supplementary.
大黒柱 is used specifically for the person who is the main breadwinner or pillar of a family, whereas 支柱 can refer to any supporting pole or figure, physical or metaphorical.
支柱 is a general support post or prop (e.g. for plants or scaffolding), while 杭 specifically refers to a pointed stake or pile driven into the ground.
支柱 is a general term for a pillar or supporting post, while 突っ張り refers specifically to a temporary prop or brace wedged in to hold something rigid.
支柱 literally means a supporting pillar and is used for the central support of a plan or group, much like バックボーン in its metaphorical sense.
支柱 (shichū, "prop/post/pillar") is long and thin, so it's counted with 本 (hon).
prop word
Compound of 支 (support) and 柱 (pillar). The exact historical derivation is uncertain, but the kanji directly reflect the meaning of a supporting pillar or prop.