The 25-year-old has joined the Pilgrims on a permanent basis after leaving Silverlands.
Smart has plenty of National League, National League North and National League South experience to his name - having featured for the likes of Eastleigh, Havant & Waterlooville, FC Halifax Town and Brackley Town.
The Portsmouth-born left-sider is registered and eligible to make his debut against Brackley on Saturday - having been allocated squad number 20 at the Jakemans Community Stadium.