So I've started a study on this topic and so far I've looked up sexy according to today's standard.
Sexually suggestive or stimulating
Why on Earth would I want to sexually stimulate or cause my brother to have impure thoughts?
And then I went to the Word.
Romans 12:1 I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service. 2
And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
Am I truly treating my body as a living sacrifice if I am causing my brother impure thoughts? Do I even want that kind of attention?
1 Corinthians 6:19 Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; 20you were bought at a price. Therefore honor God with your body.
From the passages that I've read immodesty is connected with pride and sexual immorality. This leads me to believe that by dressing immodestly, I am sewing seeds of sexual immorality and pride into my spirit and heart. I can not glorify God with a prideful heart and I cannot say that I love my neighbor if I am causing them to lust with their eyes. Sin begins with first seeing/hearing and then thinking about it and finally acting on it. Do not cause your neighbor to fall!