agglomerate

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

• transitive & intransitive verb To form or collect into a rounded mass.
• adjective Gathered into a rounded mass.
• noun A confused or jumbled mass; a heap.
• noun A volcanic rock consisting of rounded and angular fragments fused together.

from The Century Dictionary.

• To collect or gather into a mass.
• To gather, grow, or collect into a ball or mass: as, “hard, agglomerating salts,”
• Gathered into a ball or mass; piled together; specifically, in botany, crowded into a dense cluster, but not cohering.
• noun A fortuitous mass or assemblage of things; an agglomeration.
• noun In geology, an accumulation of materials made up chiefly of large blocks “huddled together in a pell-mell way, without regard to size, shape, or weight.”

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

• intransitive verb To collect in a mass.
• transitive verb To wind or collect into a ball; hence, to gather into a mass or anything like a mass.
• noun A collection or mass.
• noun (Geol.) A mass of angular volcanic fragments united by heat; -- distinguished from conglomerate.
• adjective Collected into a ball, heap, or mass.
• adjective (Bot.) Collected into a rounded head of flowers.

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

• adjective Collected into a ball, heap, or mass.
• noun A collection or mass.
• noun geology A mass of angular volcanic fragments united by heat; distinguished from conglomerate.
• noun meteorology An ice cover of floe formed by the freezing together of various forms of ice.
• verb To wind or collect into a ball; hence, to gather into a mass or anything like a mass.

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

• adjective clustered together but not coherent
• noun volcanic rock consisting of large fragments fused together
• noun a collection of objects laid on top of each other
• verb form into one cluster