To get up from sitting; to stand up.
講演が始まる前に、全員立ち上がって腰を上げた。
Before the lecture began, everyone stood up.
長時間座っていたので、立ち上がって腰を上げた。
Having sat for a long time, I stood up.
彼はソファから腰を上げて、窓の方へ歩いて行った。
He rose from the sofa and walked toward the window.
To (finally) start doing something; to take action after delay or reluctance; to get off one's backside.
長年放置していたプロジェクトにようやく腰を上げた。
He finally started the project that had been left untouched for years.
先生に言われて、重い腰を上げて勉強を始めた。
After being told by the teacher, he reluctantly got down to studying.
寒くて出かける気にならなかったが、やっと腰を上げて外出した。
It was cold and I didn't feel like going out, but I finally got moving and went out.