This is the 287th most frequent Hindi word.
कमर
Waist.
Here, 'कमर' refers to the waist or lower back area, highlighting its anatomical meaning.
मेरी कमर दर्द कर रही है।
My back is aching.
In this instance, 'कमर कसना' is an idiomatic expression meaning to prepare or get ready with determination.
उसने मेहनत से कमर कस ली।
He tightened his waist with determination.
Here, 'कमर' refers to the waist, used to describe the depth of water.