What parts of the Spanish-speaking world regularly use the word genial? Is it only encountered in Spain, or is it common in other regions as well?
It seems like it's more widespread than I realized, despite I've rarely (or never) heard it used during visits to Central America.
"Genial" is widely understood in all spanish speaking countries as it is a fairly common word.
But for usage there are many differences in how often it is used. (In common speech, speaking with friends etc...)
Spain, Argentina, Peru and Mexico generally use "genial". (Mexico uses chido as well and Spain molón)
But some other countries don't use it as often such, as
Colombia: uses more chévere or chimba or bacano (depending on context)
Ecuador: uses more arrecho (Can have a sexual meaning but is mostly to express genial or cool. ie. Qué arrecho!
This answer is rather incomplete as I can't know every country, but I can attest for those countries.
Genial is used by all the countries that use spanish as a primary language, as it is actually a word with a meaning (i.e not a slang word), you can see its definition here by the Real Academia Española which is pretty much the most reliable source whenever you have a doubt about a word, it is common in Mexico and other South American countries where I've been.
It's quite used in Argentina, coloquially, sometimes as an adjective but more as an adverb or isolated interjection (vrey much like 'great' in english).
