I like the standard definitions of grace.

The AWANA definition:  God’s Riches At Christ’s Expense

The textbook definition: unmerited favor

Both are good.  But they are lacking.  They lack in take home practicality.  Here is a definition I heard and have now officially stolen.

Grace is being fully known by God, yet still fully loved by God.

Think about it.  God fully knows everyone.  He knows our murderous, slanderous, adulterous, etc. thoughts and actions.  For those of us who have put our trust in Christ, we are still fully loved by God!  That is real grace.  It is not cheap because it sent Jesus to the cross.  It is not empty because he knows of our real sin and sins.  It is grace because we don’t deserve his love, yet he gives it fully and completely. 

Grace, grace, God’s grace,
grace that will pardon and cleanse within;
grace, grace, God’s grace,
grace that is greater than all our sin!