1. To pour or release (something) out (from or into something) in large amounts. A noun or pronoun can be used between "sluice" and "out." He turned the crank on the canal lock and watched the water sluice out. Engineers have been trying to sluice water out of the reservoir at an accelerated pace in anticipation of the heavy rainfall that has been predicted.
2. To clean, rinse, or flush the insides of something with a large flow or stream of water. A noun or pronoun can be used between "sluice" and "out." We'll need to sluice out these old pipes before we can use them again. Go to the old spigot and sluice out these slop buckets for me.
sluice something out
to rinse something out; to flood the inside of something to clean it. Sluice the wheelbarrow out, will you? Please sluice out the wheelbarrow.