Definitions for venial sin
Random House Webster's College Dictionary
a sin that does not deprive the soul of divine grace either because it is a minor offense or because it was committed without full consent or understanding of its seriousness.
Ref: Compare mortal sin.
* Rom. Cath. Ch..
Origin of venial sin:
a pardonable sin regarded as entailing only a partial loss of grace
A sin that is not a mortal sin; a sin that is not grave, or was not deliberate or was committed without a full understanding of the consequences.