From Merriam-Webster online:
1 : of, relating to, or having the characteristics of a style of artistic expression prevalent especially in the 17th century that is marked generally by use of complex forms, bold ornamentation, and the juxtaposition of contrasting elements often conveying a sense of drama, movement, and tension
2 : characterized by grotesqueness, extravagance, complexity, or flamboyance
From wikipedia:
Baroque music
It should be noted that the application of the term "Baroque" to music is a relatively recent development. The first use of the word "Baroque" in music was only in 1919, by Curt Sachs, and it was not until 1940 that it was first used in English (in an article published by Manfred Bukofzer). Even as late as 1960 there was still considerable dispute in academic circles over whether music as diverse as that by Jacopo Peri, François Couperin and J.S. Bach could be meaningfully bundled together under a single stylistic term.
Modern usage
In contemporary culture the term "baroque" is also commonly used to describe any artistic style that could be extremely elaborate, ornamented or adorned. In reality, the modern usage of baroque has nothing or very little to do with classic baroque, even though many people are unaware of the distinction.