Drop off and Sack out

Drop off verb - To grow less in scope or intensity especially gradually.

Sack out and drop off are semantically related (North American) In some cases you can use "Sack out" instead a verb "Drop off". informal substitute

Sack out verb - Prepare for sleep.

Drop off and sack out are semantically related in suspend consciousness topic. Sometimes you can use "Drop off" instead a verb "Sack out".