Pronounced si-SIN-goo-ahq. The Greenlandic q represents a sound not found in English or other European languages. It's sort of like a k, but very far back in the throat using almost a glottal stop.
When I first saw this, I saw "Sissingauo". Personally, I like that much better and even took that as a name for a character. However, I would not name a child this.
They're normally not called Sissinnguaq anymore. An abbreivated form is Singua for girls, and Sissinn or Singuaq for boys. After all: who would want to be called Sissinguaq? This was originally for both of the genders. So imagine boy and girl conversing with the same name!