A rat rod is a style of hot rod or custom car that, in most cases, imitates (or exaggerates) the early hot rods of the 1940s, 1950s, and early-1960s. The style is not to be confused with the somewhat closely related "traditional" hot rod, which is an accurate re-creation or period-correct restoration of a hot rod from the same era.

Answer this question: what is the definition of a rat rod? Let's give stream of consciousness first:
This is the relevant information: A rat rod is a style of hot rod or custom car that, in most cases, imitates (or exaggerates) the early hot rods of the 1940s, 1950s, and early-1960s.
So, the final answer is a style of hot rod or custom car that , in most cases , imitates ( or exaggerates ) the early hot rods of the 1940s , 1950s , and early - 1960s.