Something big in a dream means important. How you feel in relationship with someone or something else – as when you feel small beside somebody with a ‘big’ reputation.
Something big can also mean that it is a big task, a great success, or it contains a lot of whatever it indicates, or that it is very impressive.
Idioms: Big of somebody; big brother; big difference; big fish/noise/wheel/shot; big guns; big head; big ideas; big mouth; go down big; big time; too big for shoes.
Useful questions:
Is this big enough or too big?
What is this bigness in my waking life?
How am I measuring myself against this?