A conflict in which two parties (ususally male) are vehemently disputing something of limited relevance. Generally, both parties are somewhat wrong, but each refuses to be back down for fear of being thought the have the smaller of their two penises. Similar to a pissing match, but generally, the conflict involved involves a larger element of machismo, and continues on only because neither side wants to be seen as the one who backs down.
The White House and the Conservative Right have been in a real dick measuring contest over the qualifications of this new Supreme Court apointee, Harriet Meiers.
Two or more males make a bet on how many donuts they can place and hold (for a certain pre-determined amount of time) on their penises. Whoever is victorious must give the donuts a new glazing by cumming all over them. After the donuts are "glazed", the losers of the competition must eat the donuts that belonged to the winner. This contest is a test of length and endurance.
When people obsessively compare themselves to each other to see who is 'the best' or 'the biggest'. It may or may not involve actual penises, but it can. Usually the things being compared are worthless and meaningless things like income, car size, house size, job performance, sports stats, partner attractiveness, and yes, of course, penis sizes.
They're all bragging about how big their cars are versus the other guy's car, they're just engaging in a useless dick measuring contest.