突っ張る
つっぱる · tsupparu · JLPT N1 · verb-godan
to thrust
突っ (thrust hard) + 張る (stretch taut) = push back and stay stiff
突っ is an intensifying form of 突く (to thrust), and 張る means to stretch taut. Thrusting against something and holding it tight gives the senses of support, stiffening, and refusing to yield.