A pill was a small dosage of medicine.
To prevent Spock from following him in his pursuit of Gary Mitchell and Elizabeth Dehner, Kirk instructed Dr. Mark Piper not to give him a pill to bring him out of his unconsciouness until after he'd left. (TOS: "Where No Man Has Gone Before")
Negative use Edit
After going for a period of time without the Venus drug, Magda and Ruth demanded the pills from Harcourt Mudd. He found them in his mattress. Later, Eve took what she believed to be the pills, only to find out that they had been replaced with colored gelatin. (TOS: "Mudd's Women")
Metaphorical usage Edit
Spock referred to the as-yet-unknown to him cure-all agent that Leila Kalomi was taking him to see as a "happiness pill", something which he believed a scientist like her would know to be impossible. (TOS: "This Side of Paradise")
When McCoy described his odd meeting with Alice and the White Rabbit on the Shore Leave Planet to Kirk, he mistook it for a ruse to get him to come down, calling it a "McCoy pill, with a little mystery sugar-coating". (TOS: "Shore Leave")