A failed attempt to make any thing/situation better. The results of which are disastrous.
Much like trying to stop water from coming out of a garden hose with your thumb.
1:"Oh man. Dave totally was totally gardenhosing trying to come up with excuses for breaking up with Carla. It was pathetic."
2:Dave thumbed the gardenhose when he told Carla "It's not you, it's me."