A tantrum or a fit was a temporary outburst or loss of emotional control, usually said of a child.
In the 2270s, in response to Spock's characterization of V'ger as a child, Leonard McCoy described the entity's attack on the USS Enterprise as Spock's child having a tantrum. (Star Trek: The Motion Picture)
In 2375, Sarina Douglas expressed her relief at spending time with Julian Bashir's fellow Deep Space 9 crewmembers rather than her fellow Institute patients. She commented, "I felt so comfortable around them. I didn't have to worry that someone was going to throw a tantrum, or break into tears all of a sudden." Bashir assured her that they only exhibited that behavior during staff meetings. (DS9: "Chrysalis")
Later that year, Norvo Tigan described his behavior to his sister Ezri Dax as self-pity manifesting in the form of tantrums. (DS9: "Prodigal Daughter")