I came across the following definitions by accident when I was researching rock climbing in Spain on the website www.andalucia.com. These definitions made me smile and so I thought I should share them.
“Those who find hiking not quite exciting enough may like to try rock climbing, which is hiking vertically upwards, mountaineering, which is hiking vertically upwards with snow, or caving, which is hiking vertically downwards (except for the return journey, which is hiking vertically upwards underground).”
the Severe climber 
Brilliant, I’m stealing that!
Thanks Dave. I’m pleased you like the post. I think it is an inspired definition and particularly like how the author made sure that they noted that you have to come up again if you go caving.
Nice. I always have called moderate trad climbing “advanced hiking.” Of course, I tend towards sport / bouldering myself, so I’m biased.