(uncountable) A spicy Peruvian sauce, often containing tomatoes, cilantro, hot peppers, and onions.
In Peru the consumption of aji is greater than that of salt[…] 1847, Johann Jakob von Tschudi, Travels in Peru:
(countable) A chili pepper, in the context of South American cuisine.
Add the onion, the garlic, the red pepper, the ajies, the pepper, cumin and salt. 1997, Antonio Montaña, Gloria Mercedes Duque, The Taste of Colombia, page 47:
A horse mackerel, especially the Japanese horse mackerel, Trachurus japonicus
Although aji are found in temperate waters around the world, if you have the fish in a sushi-ya here, it almost certainly was caught and frozen in Japan. 2010, Dave Lowry, The Connoisseur's Guide to Sushi, ReadHowYouWant.com, →ISBN, page 77:
(qualifier:go, uncountable) The ‘flavour’ of a position, i.e. the extent to which it has lingering possibilities such as bad aji which may not be exploitable when they first arise yet still influence further play; good aji generally means there are few weaknesses.