(2) (noun) A way of describing a previous evening, or party- if said event led to the conquest of an improbably attractive woman, or if the ratio of such women to men was unusually high- said event/evening can be described as being a 'Girthquake'. In the event of such an evening leading to a secondary event (such as an afterparty) where a further woman (or cluster of extremely attractive women) who rate highly on the Dichter scale is discovered, then the term 'Aftercock' can be substituted.
MAN2: (adopting scientific expression) "In my opinion at least a 7 on the Dichter scale. Be careful, there is a strong chance of an 'Aftercock'"
(stands, switches to Roger Moore expression and approaches woman)
Craig: #OMG EARTHQUAKE!!!!
Marco: it was only a little girthquake you attention seeking whore
2. the shaking, trembling effect one may experience during or after sex with a person who has a large penis.
The size of his unit caused a girthquake. The aftershocks caused my legs to shake for hours.
2. having sex with a girl that has a seizure upon penetration and tilting her head and riding the aftershocks out keeping in mind to not let her choke on her tounge
2. omfg i stuck my dick in this girl and she had a seizure,so i held on and kept fucking her....i survived the girthquake