When a moment goes from that cute kind of awkward to one where you think you're being seen as a creepy serial killer. Portmanteau of retarded and awkward.
Oh my god, everything was fine until I made a joke that sounded like I was hitting on her mom and then I felt really retawkward.
Raising the awkwardness of a situation or event, typically intentionally brought on by a former lover to make you uncomfortable in a social setting, to an absolutely retarded level of awkward, thus reversing the discomfort and regaining control of the environment.
Sheila decided to parade her new boyfriend in front of John just two days after they broke up, so John got retawkward and kissed her in front of everyone.