I'm with Eric on this, but exactly because of all the possible descriptions many listed by Mark there, none of which are definitive...if pressed, I describe my boat as a
'trawler style coastal cruiser'...period..!
Peter - Time permitting, that's a comprehensive, explanatory
tag to put on a boat such as yours or mine.
However, if Captain making an emergency call due to item such as heart attack
for the captain, while motoring solo adult with a young kid aboard... the captain might die before getting out that four word description. And, if the receiver of the mayday asked "please repeat that"... well..... LOL
So... although I never have had to blast out a mayday, if it did become needed, I'd first say "34' Boat"! That's descriptive enough to get the rescuers immediately dialed into what size vessel is in trouble. After starting with that "34' Boat" statement, if I'm still alive, I would answer questions the receiver may ask.
I know from discussions with boaters at docks and on the water that I can never recall our 34' Tollycraft tri cabin being called a "yacht", in any sense. It has often been referred to as a nice "boat" or "cruiser".
For landlubbers not at all versed in marine doings, when shown a picture of our Tollycraft, the word "yacht" is often used in their first sentence... Such as, "Wow, what a beautiful yacht you have there!" Landlubbers also use the word "boat" included with or in place of "yacht" during their spoken paragraphs.
All in all: The word description of a floating craft is not so much want you know... but, rather what the other person either immediately wants to know (e.g. a mayday assistance receiver) - or - what a person thinks they immediately know (e.g. a landlubber)!
Happy Boat-Model-Name Daze! - Art