cremnophobia I can only guess how to say this.
A morbid dread of precipices or steep places.
Despite the troop leader's insistant claims that the "climb" up the mountain would be nothing more than a mild uphill walk, Henry refused to join the rest of the Boy Scouts on their exploration hike due to his gut-clenching cremnophobia.
I remember having to to on hikes in Girl Scouts. Those "mountains" really were just big hills. No climbing whatsoever. What a disappointment...