"I have a great job."
Translation:Yo tengo un gran trabajo.
Grande after the noun can mean big, large: Tengo una casa grande.
Before a singular noun it gets shortened to gran and can mean great. Ella es una gran mujer.
When does a describer come before the object? In every other case I can think of the desciber comes after the object being described except for this case.
'grande' is one of the meaning changing adjectives. When placed before a masculine noun it is shortened to 'gran' and means 'great'. When placed after it means 'big'.
un gran trabajo = a great job
un trabajo grande = a big job