trickling filter

noun

: an artificial bed of broken rock or other coarse material through which sewage or industrial wastes trickle after being sprayed on intermittently so that organic matter present is oxidized and removed by biological growths formed on the surfaces of the rock

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!