What is "thranduil"

Thranduil is a fictional character in J. R. R. Tolkien's Middle-earth legendarium. He is a supporting character in The Hobbit, where he is referred to as the "Elvenking," and he is referenced briefly in The Lord of the Rings, The Silmarillion, and Unfinished Tales. Tolkien describes Thranduil as having a crown made of red leaves and berries in the autumn, and wearing a similar crown of flowers in the spring. Like all of the Sindar, he would have been beardless, tall, and grey-eyed. The name 'Thranduil' means 'vigorous spring' in Sindarin.