Shon-ha'lock, or "the engulfment", was the Vulcan term for what Humans called "love at first sight". Tuvok described it as the "most intense and psychologically perilous form of eros".
In 2373, Tuvok characterized Harry Kim's feelings for Marayna as shon-ha'lock. As Marayna was believed to be a hologram at the time and thus no relationship was possible, he recommended logical deconstruction followed by meditative suppression. (VOY: "Alter Ego")
When he was young, Tuvok experienced shon-ha'lock towards Jara, the daughter of a Terrelian diplomat. He overcame those emotions under the tutelage of a Vulcan master. (VOY: "Gravity")