clumsy, artless

つたない Clumsy or artless – usually used about language. “Please excuse my clumsy Japanese!” Is a very Japanese way to brag about your skills, because presumably only a very advanced speaker would known what つたない even means.
 
ちせつ Clumsy or artless – usually used about artworks. “Pollock and Picasso suck! Their paintings are all sloppy! ちせつ! My three year old could paint better.”   LIT