noun
: a tuff deposit sufficiently thick and hot at the time of emplacement that the fragments soften and coalesce to form a rock which simulates rhyolite or obsidian
noun
: a tuff deposit sufficiently thick and hot at the time of emplacement that the fragments soften and coalesce to form a rock which simulates rhyolite or obsidian
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012