From Longman Dictionary of Contemporary Englishguanogua‧no /ˈɡwɑːnəʊ $ -noʊ/ noun [uncountable] TASsolid waste from sea birds, put on soil to help plants grow
Examples from the Corpus
guano• It may be the most majestic bird guano in Southern California.• Farther south, the millions of seabirds that normally nourish on the famous guano islands are being decimated.• High winds and steep rocks make landing hazardous, and the smell of guano deposits can be significant!• Fishermen scurry all over the seas catching anchovies; quarrymen have long made a living scraping guano from the bird-rich islands.• Everywhere was thick with greenish slime and off-white guano in this great bird slum.Origin guano (1600-1700) Spanish Quechua huanu 