deadlock

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

• noun A standstill resulting from the opposition of two unrelenting forces or factions.
• noun Sports A tied score.
• noun Computers A failure or inability to proceed due to two programs or devices both requiring a response from the other before completing an operation.
• noun Chiefly British A deadbolt.
• transitive & intransitive verb To bring or come to a deadlock.

from The Century Dictionary.

• To bring to a dead-lock or standstill: as, “they have dead-locked the legislature,”
• noun A lock with a key-bolt, but with no latch-bolt, operated by a knob.
• noun A lock in which the key-bolt must be moved by turning the key in each direction: distinguished from a spring lock.
• noun A lock worked on one side by a handle and on the other side by a key.
• noun A complete stoppage, stand-still, or entanglement; a state of affairs in which further progress or a decision is for the time impossible, as if from an inextricable locking up: as, a dead-lock in a legislature where parties are evenly balanced.

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

• noun A lock which is not self-latching, but requires a key to throw the bolt forward.
• noun A counteraction of things, which produces an entire stoppage; a complete obstruction of action.

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

• noun A standstill resulting from the opposition of two evenly matched forces; a stalemate or impasse
• noun computing An inability to continue due to two programs or devices each requiring a response from the other before completing an operation
• verb to cause or to come to a deadlock

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

• noun a situation in which no progress can be made or no advancement is possible