Tiamat’s Multiple Heads feature gives her reactions. Is a melee?

#DnD folks who have run Rise of Tiamat: Tiamat's Multiple Heads feature gives her reactions, but doesn't say what she does. Is is a melee?

— Teddy Yudain (@Tsyclops) April 18, 2016

Tiamat's Multiple Heads lets her take extra reactions to do normal reactive things, like opportunity attacks. #DnD https://t.co/WwLeEgCZB9

— Jeremy Crawford (@JeremyECrawford) April 19, 2016