Semi
Those big trucks that get around, we call them semis which is short for semi-articulated.
The front part is the “cab” and the rear part is the trailer.
The “articulated” is because they have two or more sections (cab and trailer) connected by a flexible joint.
The semi is because the trailer only has wheels at the back.
So the “semi-articulated” is nonsensical – there is no half articulation going on.
Well there is actually, but it’s the trucker English that’s the culprit.