There are different interpretations for this phrase and several have reasonable arguments supporting them.
I take it this way:
Earlier in I Cor, Paul tells the Corinthians that they will ultimatley judge angels.
Since angels ultimately will be ranked lower than humans, women should show proper submission in the church (to men or to their husbands--that's another question).
It is not fitting that those who are to rank above angels in the future should themselves refuse to demonstrate submission in the present.