Commander Kor likened the situation he and Captain James T. Kirk experienced together on Organia as being "on a planet of sheep" with them being "two tigers, predators, hunters, killers, and it is precisely that which makes us great." (TOS: "Errand of Mercy")
The term was used in a metaphorical sense on a number of cases:
After Leonard McCoy recovered from his cordrazine-induced madness, Edith Keeler, who believed he was sobering up, told him, "You're not ready to take on any tigers just yet. Lie down." (TOS: "The City on the Edge of Forever")
When the Beta XII-A entity had taken over the USS Enterprise in 2268, while carrying a load of Klingon warriors, Nyota Uhura was unable to make contact with Starfleet Command, Kirk informed her to keep trying, reminding her that "We've got a diplomatic tiger by the tail." (TOS: "Day of the Dove")
As a respectful insult, Midshipman 1st Class Peter Preston told Admiral Kirk that if he couldn't see that the USS Enterprise had the best engine room in all of Starfleet, then he was "as blind as a Tiberian bat," Kirk smiled and responded by telling the midshipman that he was "a tiger." (Star Trek II: The Wrath of Khan)
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In the final draft script of TNG: "The Outrageous Okona", Thadiun Okona, after referring to Wesley Crusher as "Wesley, Wesley Crusher" and "Ensign Crusher, Crusher", continued to tease Crusher by stating "I'll make it easy on both of us. I'll just call you "Tiger"."
A number of characters were compared to tigers in various scripts:
During the fight between Roga Danar and Worf in TNG: "The Hunted", the script specified that "Roga fights like a cornered tiger, finally gets the upper hand, drops Worf with a massive two-handed blow. Worf sags, nearly unconscious."