zest

Short definition from Wiktionary

Noun

1. 1
   The outer skin of a citrus fruit, used as a flavouring or garnish.
2. 2
   General vibrance of flavour.
3. 3
   Enthusiasm; keen enjoyment; relish; gusto.
4. 4
   The woody, thick skin enclosing the kernel of a walnut.
5. 5
   State of being effeminate or a flamboyant homosexual.

Verb

1. 1
   To scrape the zest from a fruit.
2. 2
   To make more zesty.