An idol or icon was an object or person of worship.
The Vulcans had idols in form of statues they kept in different places such as shrines in a monastery as the one at P'Jem in 2151. (ENT: "The Andorian Incident")
In 2266, James T. Kirk criticized Robert Crater for harboring and protecting the dangerous M-113 creature, saying, among other things, it was an idol to him. (TOS: "The Man Trap")
According to Data, the Taqua Tribe of Nagor saw an hammer as an icon of hearth and home. (TNG: "Birthright, Part I")
Kira Meru, mother of Kira Nerys, was an icon painter from Dahkur Province. (DS9: "Second Skin")
The most revered icon of Klingon history was the Sword of Kahless, an icon that predates the Klingon Empire and an icon more sacred than the Torch of G'boj. (DS9: "The Sword of Kahless")
In 2373, Kira Nerys told Jadzia Dax that she was looking at the most important Bajoran icon ever painted, a painting of the city of B'hala. (DS9: "Rapture")
In 2374, Jadzia Dax told Benjamin Sisko that it would make Starfleet very uncomfortable that Sisko allowed the Bajorans to see him as a religious icon, the "Emissary of the Prophets". Sisko previously told Dax that is is sometimes hard to be a religious icon. Major Kira previously told Sisko that it was hard to work for an icon. (DS9: "Destiny", "Accession", "The Reckoning")
Klingon golden idol
In 2381, Beckett Mariner retrieved a golden Klingon idol from Ferengi grave robbers. She and Petra Aberdeen then brought it to the Qualor Historical Museum. (LD: "The Stars At Night")