A strapless dress doesn’t have shoulder straps.
This is a very popular dress among women for Gala Events.
Celebrities love to wear them for Red Carpet Events.
Here are a few examples of strapless dresses.
This is Amy Adams at the Golden Globe Awards 2013. You can also observe that this dress is also a mermaid gown and the designer is Marchesa. It is not the first time that this star wears a dress from this designer, in the same event in 2011 she picked a dress from the same designer.
For the same Event Kelly Osbourne also picked a strapless, mermaid dress designed by Zac Posen.