A puddle was an amount of liquid concentrated in one small area, such as a hollow in the ground.
In 2268, following several phaser shots ordered by Spock, Montgomery Scott commented, "That Vulcan won't be satisfied till these panels are a puddle of lead." (i.e. Spock would continue firing until the control panels melted.) (TOS: "The Paradise Syndrome")
In 2364, Tasha Yar reported that security team two found a puddle of blood outside the guest quarters assigned to the Selay delegation. (TNG: "Lonely Among Us")