Definitions of rat
The word "rat" uses 3 letters: art.
n. - One of several species of small rodents of the genus Mus and allied genera, larger than mice, that infest houses, stores, and ships, especially the Norway, or brown, rat (M. decumanus), the black rat (M. rattus), and the roof rat (M. Alexandrinus). These were introduced into America from the Old World. 2
n. - A round and tapering mass of hair, or similar material, used by women to support the puffs and rolls of their natural hair. 2
Words formed by adding one letter before or after rat (in bold), or to art in any order:
i - airt s - arts rats star tars tsar y - arty tray b - brat c - cart d - dart drat trad f - fart frat raft g - grat h - hart rath tahr k - kart m - mart tram p - part prat rapt tarp trap n - rant tarn e - rate tare tear o - rato rota taro tora t - tart z - tzar w - wart