1. What does it mean?
맛도리 is a friendly internet-food expression for something particularly enjoyable to eat. It can stand alone as a noun-like compliment or appear in 이거 맛도리다, meaning this is really tasty.
Also written or said as matdori
2. The nuance
It is informal and playful rather than a precise flavor description. Claims about its exact first origin vary, so the useful point is its current appreciative food meaning.
3. Examples
“남은 채소로 만들었는데 의외로 맛도리네.”
I made it with leftover vegetables, but it's surprisingly delicious.
“이 조합은 내 기준 확실한 맛도리야.”
For my tastes, this combination is a definite winner.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.