Two individuals with a penis, counteracting their exposed cocks in synchronous alternating directions (without touching), resembling the rotation of the blades of a Chinook helicopter.
To those making sexual definitions about this, you are the most retarded dudes I have ever met. A Chinook is a heavy, dual rotored transport helicopter that has a top speed that is almost 200 MPH. Primary use is to transport infantry and/or vehicles. In Call of duty they have replaced the little bird helicopters for the care package delivery. it is slower and is a bigger target in BO so one can shoot it down and steal the package.
A rotary winged aircraft (helicopter) produced by Boeing/Vertol, it is very distinctive, having two counter rotating rotors rather than the main rotor/tail rotor setup of most helicopters. A powerful heavy-lifter, the first version introduced during 'nam could carry about six tons, the latest versions (e, f) can carry over twelve. The aircraft is designated CH-47. (CH stands for Cargo Helicopter)
The sound of a chinook is very distinctive, like some enormous jackhammer, a penetrating basso thunder that can be heard miles away, and makes the earth shake when the aircraft passes close by.