a rope attached to the bow of a boat for tying it as to a dock

There is a lovely harbor at Rye, NH, with a many-windowed restaurant on the shore.(Sanders, if your near there) and it is a source of amusement to those sea-wise among us to see newcomers tie their small painter up to a stanchion and debark for lunch and a few drinks ... while the tide goes out ... and return to find their boat high and dry, hanging alongside the stanchion and not a prayer of going anywhere until the tide comes in again.... about 8 to 12 hours before it's high enough to float your boat!
The moral is : leave plenty of rope between your boat and the tie-up so you don't end up High and Dry!