A word used by Gujarati Indian women, to threaten their children when they're mis-behaving. It essentially means to hit the child, usually with a slipper, or just their hand. It isn't a form of violence, or child abuse, just a phrase used to scare a child, similar to telling a child off for being naughty.
Mum: 'STOP IT! You're not getting a toy today!'
Son: 'Please mum, pleeeeeeeease'
Mum: 'If you don't be quiet, Ek Japati Karu'
*Child stops moaning and behaves accordingly*
Son: 'Mum, mum, mum, ma, ma, ma, mummy, mummy, mummy, maam, maam, maam, mom, mom, mom...'
Son: 'Nothing (sniggers)'
Mum: 'Ek Japati Karu'
(Son shuts up and minds his own business)