noun
A pole or stick used to prop something up, such as a washing pole, a plant support, or a temporary brace for a structure.
洗濯竿がたわまないようにつっかい棒を入れた。
I put a prop under the laundry pole so it wouldn't bend.
台風の
Some houses brace their windows with a prop before a typhoon.
支柱 is a more general term for a support or prop, often used in construction or gardening, while つっかい棒 specifically refers to a pole or stick used as a temporary brace.
Compound of つっかい (continuative form of つっかう, 'to prop up') + 棒 (ぼう, 'stick, pole'). The exact origin of つっかう is uncertain, but it is likely related to 突く (つく, 'to thrust').