A big, tall car built to look like it can drive on rough roads — mud, snow, dirt tracks. SUV is short for 'sport utility vehicle', but almost nobody says the full words; you say the three letters, S-U-V. The word points at a shape more than at a fact: high off the ground, big body, room for five to seven people, a large door at the back that lifts up. Here is the 'though actually' part — most SUVs never go anywhere rough. People buy them for city life: the seat is high so you see over other cars, there is space for children and bags, and many people say they feel safer up there. Car sellers know this, so now there are small SUVs that are really just a normal car made taller, and you will hear people argue about whether those 'count'. That argument tells you the word has stretched. It is a plain, everyday word — no formality either way. You say 'an SUV', not 'a SUV', because you are saying the letter S, which starts with an 'e' sound.