The act of oral sex given to a man while the woman uses both her hands at the same time to grip the shaft and simultaneously stroke and twist as she sucks.
A man of adequate penis length and a woman of excellent skill is needed to pull off the dually.
The wife was too tired to fuck last night but she gave me a wicked dually.
I brought home flowers for the old lady and got a dually in return.
Woke up this morning and caught a dually before work.
Screwing a girl on the toilet while both of you are taking a shit.
When you are taking a shit a girl comes and sits on your cock and takes a shit as well. This takes extreme concentration on both parts.