what is the definition of breakeven point?

Break even point can be defined as the point where the total cost of the firm is exactly equal to its total revenue. At this pint the firm earns zero economic profits. 

In order to read more on break-even point refer to Chapter-4 (The Theory of The Firm Under Perfect Competition), Lesson-4 (Equilibrium and Perfect Competition – Short Run and Long Run) , Topic- Short Run Producer's Equilibrium.