the GNU version of the Collaborative International Dictionary of English
noun-plural. Small crimson, purple, or livid spots, like flea-bites, due to extravasation of blood, which appear on the skin in malignant fevers, etc.
The Century Dictionary and Cyclopedia
Purple spots on the skin, not disappearing on pressure, caused by hemorrhage into the cutaneous tissues.
Word Usage
"The way, I guess, that they scale the condition of the patient is through the amount of petechiae, which is blood vessels that have been broken in the eyes, under the eyes, on the eyelid."