coalesce

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

• intransitive verb To come or grow together into a single mass.
• intransitive verb To come together as a recognizable whole or entity.
• intransitive verb To come together for a single purpose: synonym: mix.
• intransitive verb To cause to coalesce as a single mass.
• intransitive verb To cause to coalesce as a single whole or entity.

from The Century Dictionary.

• To grow together; unite by growth into one body.
• To combine or be collected or joined, so as to form one body.
• Hence To come or join together; unite so as to form one party, community, or the like: as, political parties sometimes coalesce.

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

• intransitive verb To grow together; to unite by growth into one body.
• intransitive verb To unite in one body or product; to combine into one body or community.

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

• verb of separate elements To join into a single mass or whole.
• verb of a whole or a unit To form from different pieces or elements.
• verb engineering When two, or more, pieces of metal are bonded together (usually via welding) by liquefying the places where they are to be bonded, coalescing these liquids, and allowing the coalesced liquid to solidify. At the end of this process the two pieces of metal have become one continuous solid.

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

• verb fuse or cause to grow together
• verb mix together different elements