Not so dusty British old-fashioned adjective
Used to describe something is fairly good or acceptable
I think my English is not so dusty.
My cooking skill is not so dusty. I just know to cook basic dishes.
Used to indicate satisfaction or approval in a litotical manner
Used to imply that someone is acting as if he or she is demure, innocent, sincere or reserved but they may be not
Don’t be fooled by Jennie's good behaviour. She looked as if butter wouldn't melt in her mouth.