Commander Kor likened the situation he and Captain James T. Kirk on Organia together as being "on a planet of sheep" and they were "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 a deleted scene taken from the final draft of TNG: "The Outrageous Okona", Okona continued the tease Wesley with the bit of near the opening of the episode, when he was introduced to "Wesley Wesley Crusher", stating "I'll make it easy on both of us. I'll just call you "Tiger"." At that moment Data entered and stated "Captain Picard is not fond of nicknames."
A number of characters are compared to tigers in various scripts.
When the Ferengi first see their first human female, Tasha Yar, who just demonstrated her phaser skills, in TNG: "The Last Outpost", it was stated in the script notes that "the Ferengi are handling this with all the astonishment of seeing man-eating tigers."
In another instance, during the battle between Roga Danar and Worf in TNG: "The Hunted", it was stated that "Roga fights like a cornered tiger, finally gets the upper hand, drops Worf with a massive two-handed blow. Worf sags, nearly unconscious."
A later instance yet, when the crew of the Defiant is captured by the Jem'Hadar in DS9: "One Little Ship", and the crew are herded into the mess hall, it was stated that "Worf paces the room like a caged tiger."