허리가 · 허리를
waist, lower back
Example
오래 앉아 있어서 허리가 아파요.
My lower back hurts because I sat for a long time.
Word parts
허리띠 = belt (literally 'waist band').
Good to know
허리 covers both the waist and the lower back: 허리가 아파요 usually means 'My back hurts.'
Related words