'Omnibus' may be more familiar, but 'charabanc' will likely be challenging to younger native speakers too. And then in this category there are the 'brougham', '

'Omnibus' may be more familiar, but 'charabanc' will likely be challenging to younger native speakers too. And then in this category there are the 'brougham', 'phaeton', 'trap', 'hansom', and 'dog-cart', the latter of which can of course refer to a cart pulled by a dog, but often means yet another type of horse-drawn carriage. I fully expect most readers nowadays will just go 'ah, they got into some conveyance pulled by horses' rather than having a clear image of the specific carriage referred to. Reading works by Charles Dickens, Arthur Conan Doyle, Wilkie Collins, etc. really expands your horsey vocabulary.