The best replacement for gown is dress.

The best alternatives to gown are rated as following:
★★★★★  dress
★★★  cocktail dress
★★  frock
★  robe
★  housecoat
★  mermaid
★  bathrobe
★  wedding dress
★  italian town
★  negligee
  prismatic dress
  say yes to the dress
  town
  a-line
  sleep sack
  evening gown

Your alternative for gown is not listed? Suggest!
Speaking about gown, one probably shouldn't forget about bolero.

Other search terms related to gown and their ratings are:
★★★★★ bolero
★★ veil
You have in mind a companion for gown and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gown in all years. Click on graph for more.
gown
dress
cocktail dress