As described in TheSoulOfaNewMachine, the act of a member of a team making an informal but significant commitment to the successful completion of a major project. 

From the book:  ''By signing up for the project you agreed to do whatever was necessary for success.  You agreed to forsake, if necessary, family, hobbies, and friends - if you had any of these left (and you might not if you had signed up too many times before).''

Perhaps an extreme form of "owning" a task.

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See also: TakeResponsibility, PlaySoldier