What is undertaking?
“Undertaking a car” usually refers to overtaking a vehicle on its offside (usually the right in countries that drive on the left, or the left in countries that drive on the right)—essentially passing it on the side that’s normally considered the “wrong” side for overtaking.
In most places, undertaking is discouraged or illegal because it can be dangerous: drivers don’t expect a vehicle to pass on that side, and it can lead to collisions.
For example:
• In the UK (driving on the left), undertaking means passing a car on its left.
Illegal in the UK