Sour. It is more noticeable the stronger the brew. I like the stronger sour where the jaws ache. The weaker sour reminds me of staleness where something has sit too long. I never took stock in describing teas or reading what others say. I have recently started to analyze tea according to the five taste sensations bitter, sweet, salty, sour, umami or sometimes called savory. So far most fit in one category or another. The closest Ive come to unami or savory is DianHong which otherwise I would call rich and complex so I dont know if a simple taste is appropriate. I always say there is no accounting for taste buds but the science says you can.
Jim