be on the rocks

1. Literally, to have become stuck on rocks in the water, as of a ship. Our ship is on the rocks now, after crashing during that violent storm. Captain, we're on the rocks! What do we do? No one was hurt in the crash, thank goodness, but our ship's still on the rocks.

2. To be in jeopardy and likely to end or fail. Typically used in reference to romantic relationships. Did you hear that Bill and Maria are on the rocks? Of course their marriage is on the rocks, they fight all the time! Our project is on the rocks because the committee pulled their funding.

3. To suffer financial hardship, often suddenly. I was on the rocks pretty soon after I lost my job. You need to make sound financial decisions to keep your company from being on the rocks. Many people were on the rocks after that massive stock market crash.

4. To contain ice, as of an alcoholic beverage. That drink's on the rocks, so it's not the one I ordered. Sir, you wanted a scotch, right? Is that on the rocks? I don't like when drinks are on the rocks. The ice melts too fast and waters everything down!

on the rocks, to be

Ruined, either financially or in some other way. This term comes from a ship that has run aground on rocks and will break into pieces unless it can be hauled or floated off in time. The term began to be used as a metaphor for other disasters in the late nineteenth century. A common modern application appears in Tennessee Williams’s play Cat on a Hot Tin Roof (1955): “When a marriage goes on the rocks, the rocks are there, right there [pointing to the bed].” A more recent meaning for on the rocks is for a beverage, usually containing liquor, that is served over ice cubes (“rocks”).