The meaning comes from riding mopeds, which are typicaly a slow form of transport. To get them to go faster, a rider can reduce their profile and improve their aerodynamics by laying flat on the fuel tank; "tanking it".
Filling yourself with liquids e.g water to boost bodies weight for a short period of time.
often used by people with eating disorders to avoid accusations of weight loss
Tanking would be to take 'a shower' and drinkthe water before being weighed
(Australia)
This refers to a player in a computer game that is gaining excess hitpoints and armour, thereby being more difficult to eliminate by his/her enemies
I don't want to fight with my character yet. I would be tanking my hero instead