Translation:For the most part.
formhór is "majority". d'fhormhor on it's own is just "for the most part", an idiomatic expression in Irish, just as it is in English. It can also occur in a sentence where it would mean "for most" or "for the majority".
*that resolution is optimal for most drawings" - is é an taifeach sin is fearr d'fhormhór na léaráidí
"construction was the main driver of the economy" - an tógáil a bhí taobh thiar d'fhormhór dul chun cinn na heacnamaíochta
The scenarios in which you might refer to "your majority" involve politics, where they use the words tromlach or móramh, ("they hold a majority in the parliament"- tá tromlach acu sa pharlaimint), in the law ("to reach the age of majority" - teacht i lán-aois) and in the military, where the rank of major can be referred as a majority, but the Irish is maoracht.
D'fhormhór means "for the most part", or other synonymous phrases.
What dialect of English do you speak? Do you want Boston phonetics, Cockney phonetics, Cork phonetics, Melbourne phonetics, Belfast phonetics, Liverpool phonetics, Glasgow phonetics, Bronx phonetics, D4 phonetics, Tralee phonetics, Capetown phonetics?
You can hear formhór spoken here on Duolingo: https://forum.duolingo.com/comment/7510160
As fh is silent, d'fhórmhór i pronounced with a d sound replacing the f in formhór.
It's a single word comprised of multiple parts to express a single meaning. The English translation of the meaning just happens to be four words. It might be 3, 5, or 7 words in another language. You're not going to have a one-to-one translation for everything.
There are countless cases of an Irish word translating to more than one English word, or the opposite. I don't see what the problem is.