An erection that occurs in the morning and is naturally caused as the brains enters the REM-deep sleep phase. At this stage, the body's skeletal muscle structure relaxes and causes hypervasodilation in the capillaries of the body, resulting in said erection.
"Scott, this morning I had a huge breakfast boner and my first piss of the day ended up all over the walls"
an erection similar to the morning wood, only it is slightly delayed and doesnt rise until your at the breakfast table. can also refer to a morning wood erection that doesnt go down until your at the breafast table. or it can simply be used interchangably with morning wood.
Steve woke up in the morning to his surprise with no erection. However, while waiting on his pancakes Steve got a breakfast boner.