The origin of this word comes from fifa 09. After referring to ronaldinho as "Ronoldinosaur" we shortened it to "dinosaur" and then simply just to "Dickosaur". Dickosaur seemed a proper term because if you had him on your team, you would kill everybody at fifa, labeling you and your star player as a dick, or a "dickosaur".
Today, this term can always be used in everyday life. It is mostly used after somebody does something that would be considered "dick". Such as fucking your bestfriends girlfriend or eating all of the steak out of the refrigerator.
"dude your a fucking dickosaur, all you had to do was tell me that you used my beard trimmer to trim your pubes, now i have fucking pubes all over my face!"
"i can tell that your dads a dickosaur, he doesn't let you do anything and always gets you in trouble"