| Y
| Yttrium An element with the atomic number of 39 |
| Y axis
| The Y axis represents the voltage displayed on the face of the oscilloscope |
| Y-block
| The block of a V-type engine having a deep crankcase. |
| Y-pipe
| A Y-shaped pipe, such as an exhaust pipe, that merges two passages into one. |
| yaw
| 1. The Z-axis 2. The rotation of a vehicle structure around a vertical axis. |
| Yb
| Ytterbium An element with the atomic number of 70 |
| yellow bumper
| 1. Freshman driver in NASCAR competition Also known as yellow tail. 2. The color of the rear bumper of a first-year driver's car in NASCAR competition. |
| yield strength
| The amount of force that can be applied to a material before it bends or breaks. |
| yocto
| The prefix representing the number 0.000,000,000,000,000,000,000,001 |
| yoke-sleeve kit
| A kit that may be used to rebuild the yoke. |
| yotta
| The prefix representing the number 1,000,000,000,000,000,000,000,000 |