I know that the word legato means to play smooth and flowing... but this is in the general music world ... but in guitar world (I mean in tabs and notes) it's only used to refer to hammer-ons & pull-offs, and about the slide thing you mentioned, they call it 'legato slide', and if I didn't mention it , this doesn't means that I didn't know it..
And about 'glissendo' & 'slide' , I don't see any difference except for the spelling and the word 'glissendo' is Italian (not sure, but it's a europian language anyway), while the word 'slide' is English...
Plz don't reply telling me that English and Italian are both Europian languages !!
I don't know why are you trying to be very precise with this terminology, I don't like to take music mathematicaly, bec it's not a science, it's more about imagination than it is about books & education..
Don't misunderstand me, I'm studying elec. engineering, and I like science a lot, but I like to do every thing as it should be done, in my college, there is right & wrong, but here in the music world, absolutely no body is wrong , every one plays his music as he/she likes.. there ain't exist anything in the music that could be 100% right or wrong.. is there a perfect (amp/guitar/strings/effect/strings/or even a pick) that every body agrees about?! is there anything that we all agree about, from music genres, to your fav. bands , and the best guitarist, etc...
Finally, no offence , I was just saying my opinion ..