Definitions:

1. Prepare for sleep. VERB
   • The workers sacked out in the break room, taking a quick nap before their next shift.
2. Slang phrasal verb that means to go to sleep or to fall asleep, often from exhaustion or after a long day. VERB
   • After the hike, we all sacked out around the campfire.
3. To lie down and sleep, especially in a relaxed, casual, or tired state. VERB
   • He sacked out on the couch during the movie.

Synonyms:

• crash
• doze off
• go to bed
• hit the sack
• knock out
• turn in