This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Capable of being used as a substitute, valid as a replacement or alternate item.

adj. Capable of being substituted.

adj. capable of being exchanged for another or for something else that is equivalent

adj. (of words) interchangeable in a given context without changing the import of the expression

"Generics companies will need to do that if they want the FDA to deem their product " substitutable " for the original, meaning that a pharmacist could dispense the copy even if a patient had a prescription for Advair."

exchangeable    synonymous   

unsubstitutable    nonsubstitutable