This will depend on what is being done with the brassier in the dream, and what part it plays. But some general associations are that is a means to enhance attractiveness; to hide ageing breasts; as something that can be taken off to lure a man fancied.
It also can be a symbol of the breasts, of female freedom if removed, so can depict any of the huge range of feelings connected with female sexuality or emotions.
As underwear it might point to the hidden side of your nature, or of someone revealing their real feelings – especially sexual feelings and feelings of vulnerability. Or is it about getting a decent brassiere that fits?
Useful Questions and Hints:
In what way is the brassiere being presented in the dream, and what feelings are involved – and how do those feelings appear in my daily life?
If a male dream – what feelings do I have in connection with these brassieres, and where do I meet those feelings?
What are the surrounding events and the environment, and what do they add to the understanding of the dream? (i.e. is this in a hospital after childbirth – so about motherhood and the return to not being pregnant/ Is it about a sexual situation and so a comment on your relationship with sex – etc?)