1. A moral or ethical consideration that tends to restrain one's action or behavior.
2. An uneasy feeling arising from one's conscience or principle that tends to hinder action a certain less than acceptable behavior.
3. A doubt or hesitation as to what is morally right in a certain situation.
4. A minute (tiny) part or very small amount.
5. A unit of apothecary (drug store) weight equal to about 1.3 grams, or 20 grains; or 1/3 of a dram, abbreviated as, sc. or scr.
6. Etymology: coming from the 1520's, from Old French scrupule, which came from Latin scrupulus, "uneasiness, anxiety, disturbance of the conscience"; literally, "a small sharp stone"; from scrupus, "sharp stone or pebble".

This was used figuratively by Cicero for a "cause of uneasiness" or "anxiety", perhaps from the notion of having a pebble in one's shoe.

A more literal Latin sense of "a small unit of weight" or "measurement" is certified to have been in English from the late 14th century.

1. To hesitate to act, or to refrain from taking action, because of moral or ethical considerations.
2. To delay doing something because of thoughts about what is right or wrong.
3. To hesitate as a result of one's conscience or principles about doing something bad: "The man scrupled about perjuring himself; but, after he lied, he didn't scruple about it anymore."