commuterection 

The uncontrollable erections caused by the swaying of the subway, often ending in embarassing stares from fellow commuters.

I was leaning against the door, and it gave me a massive commuterection

commuterection by precid June 21, 2005

commuterection 

An unintentional, likely undesired erection caused by the wide range of vibrations encountered while riding public transportation.

Due to the questionable state of the train tracks between stations Chabanel and Parc, Jeremy received a raging commuterection and was forced to hold an umbrella in front of his crotch.

commuterection by Jerrrrr April 2, 2007

Commuterbation 

Masturbating discretely while on public transportation. Often done via pockets in trousers. More daringly, while sitting down, some individuals will even unzip their fly and insert hand into area with the concealment of a bag on lap.

I was on the subway last night and this smoking hot chick sat in front of me. I put my hands in pocket and immediately commenced vigorous commuterbation.

Commuterbation by Royds-McLloyds March 15, 2011