sit back

verb2

1. •
   To recline while still in a seated position, with one's back on the frame of the seat.

   • Please just sit back and watch the show.
   • She sat back on her haunches.
2. •
   To relax, to not exert oneself.

   • Predictably in the second half it was the Potters, who went searching for goals as Fulham sat back to defend their lead. — 2010