all hands

1. A call for all members of a ship's crew to come to the deck, usually in a time of crisis. (A "hand" is a member of a ship's crew.) We're under attack! All hands on deck! All hands on deck! Man your posts! We were all filled with dread at the sound of the command: "All hands on deck!"

2. By extension, everyone available to help with a problem, or a call for those people to help. Your grandmother arrives tomorrow and the house is still a mess—I need all hands to help me clean! All hands! We've got to roll out this tarp before the rain starts. Now let's go! Mom says she needs all hands for the garage sale on Saturday, so my brothers and I are going home to help her.

3. Describing something that requires the presence of all those involved. In this usage, the phrase is usually hyphenated. We're having an all-hands meeting tomorrow to go over the new policies, so attendance is mandatory. We need to have an all-hands gathering so we can brief the volunteers ahead of the carnival. Uh oh, things must be bad if the board is convening an all-hands meeting.

all hands

the entire crew of a ship.

A US variant of this phrase is all hands and the cook , meaning ‘absolutely everyone available’, since the cook would not normally be expected to do the work of other team members except in cases of dire emergency.