Take off all of your clothes. Go up to any town guard and perform the Vulgar Thrust at them. This will give you the achievement, and a small fine.

You don't have to have all your clothes off, just your trousers and vulgar thrust at them.

You have to strip off all your clothing and go around vular thrusting at people. With this, you have to wait until someone is so offended that they tell the town guard on you. (or just start thrusting the guard lol) Either way your going to have to give up a few coin to pay for the offense.

If you walk up to someone with no clothes on and do the 'vulgar thrust' or 'seduce' expression and you shall gain this achievement once you have been reported to the guards. Or save time and do it at a guard.

Take off all of your clothing and do the Vulgar Thrust dude!!