avalanche

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A fall or slide of a large mass of material, especially of snow, down a mountainside.
• noun A massive or overwhelming amount; a flood.
• intransitive verb To fall or slide in a massive or overwhelming amount.
• intransitive verb To overwhelm; inundate.

from The Century Dictionary.

• noun The fall or sliding down of a mass of snow or ice from a mountain-slope.
• noun Hence—2. Anything resembling an avalanche in suddenness and destructiveness: as, an avalanche of misfortunes.

from the GNU version of the Collaborative International Dictionary of English.

• noun A large mass or body of snow and ice sliding swiftly down a mountain side, or falling down a precipice.
• noun A fall of earth, rocks, etc., similar to that of an avalanche of snow or ice.
• noun A sudden, great, or irresistible descent or influx of anything.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A large mass or body of snow and ice sliding swiftly down a mountain side, or falling down a precipice.
• noun A fall of earth, rocks, etc., similar to that of an avalanche of snow or ice.
• noun A sudden, great, or irresistible descent or influx of anything.
• noun Anything like an avalanche in suddenness and overwhelming quantity (like a barrage, blitz, etc).
• verb intransitive To descend like an avalanche.
• verb transitive To come down upon; to overwhelm.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a slide of large masses of snow and ice and mud down a mountain
• verb gather into a huge mass and roll down a mountain, of snow
• noun a sudden appearance of an overwhelming number of things