Definition of "eco"

eco¹

/ˈiːkəʊ/

adjective
comparative more eco, superlative most eco
1. Clipping of ecological. Environmentally friendly or sensitive.
  Quotations
  Except that the smart eco (and fiscal) thing to do is to wait until your current appliance has reached its break-even point […]
  2008 December 28, Lucy Siegle, “Why older isn't always wiser”, in The Observer‎
  Check the eco credentials of your paint – not all are what they say on the tin.
  2019, Roger Hunt, Marianne Suhr, Old House Eco Handbook, page 156
2. Clipping of economy. Affording economical use, e.g. of an appliance.

eco²

/ˈiːkəʊ/

noun
plural ecos
1. A proposed name for the common currency that the West African Monetary Zone plans to introduce in the framework of the Economic Community of West African States.