ultracrepidarian

adjective

noting or pertaining to a person who criticizes, judges, or gives advice outside the area of his or her expertise. The play provides a classic, simplistic portrayal of an ultracrepidarian mother-in-law.

noun

an ultracrepidarian person.

origin

1800–20; ultra- + Latin crepidam 'sole of a shoe, sandal' (< Greek krepis 'shoe'); in allusion to the words of Pliny the Elder ne supra crepidam sutor judicare, 'let the cobbler not judge above the sandal'; cf. the English proverb “let the cobbler stick to his last”

http://dictionary.reference.com/browse/ultracrepidarian
https://en.wikipedia.org/wiki/Ultracrepidarianism