OST can have more than one meaning:

• OST stands for Original Soundtrack. The term can be used to describe the musical soundtrack sold for any movie or TV series, but the phrase "OST" is more often used when describing soundtracks from anime. Common purveyors of anime OSTs in the United States include ADV Music, AnimeTrax, Pioneer Entertainment (now Geneon), and Bandai.
• OST is short for the Office of Science and Technology, a British government agency.

• 'OST' is also the abbreviation and mark of the Taiwan Ostor Corporation, who commonly make Alumunium Electrolytic Capacitors (http://www.ost.com.tw). They are an accepted and well known "crap cap" brand, i.e, a company who's capacitors are sub standard.