Definition from Wiktionary, the free dictionary
See also give away
giveaway (plural giveaways)
- something that is given away or handed out for free
- The t-shirt was a giveaway from the company that sells the software.
- something that is obvious or apparent; something that reveals a secret
- The frosting in his beard was a giveaway that he had been munching the cake.
Usage notes 
- The verb to give away, is two words.
(something given away for free): freebie