any unwanted and destructive insect or other animal that attacks food or crops or livestock etc.; "he sprayed the garden to get rid of pests"; "many pests have developed resistance to the common pesticides"
any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention
(virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein
a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer; "a true virus cannot spread to another computer without human assistance"
a harmful or corrupting agency; "bigotry is a virus that must not be allowed to spread"; "the virus of jealousy is latent in everyone"
an acute viral disease of the nervous system of warm-blooded animals (usually transmitted by the bite of a rabid animal); rabies is fatal if the virus reaches the brain
a perceptible indication of something not immediately apparent (as a visible clue that something has happened); "he showed signs of strain"; "they welcomed the signs of spring"
a public display of a (usually written) message; "he posted signs in all the shop windows"
a character indicating a relation between quantities; "don't forget the minus sign"
a gesture that is part of a sign language
a fundamental linguistic unit linking a signifier to that which is signified; "The bond between the signifier and the signified is arbitrary"--de Saussure
(medicine) any objective evidence of the presence of a disorder or disease; "there were no signs of asphyxiation"
be engaged by a written agreement; "He signed to play the casino on Dec. 18"; "The soprano signed to sing the new opera"
communicate in sign language; "I don't know how to sign, so I could not communicate with my deaf cousin"
mark with one's signature; write one's name (on); "She signed the letter and sent it off"; "Please sign here"
communicate silently and non-verbally by signals or signs; "He signed his disapproval with a dismissive hand gesture"; "The diner signaled the waiters to bring the menu"
place signs, as along a road; "sign an intersection"; "This road has been signed"
engage by written agreement; "They signed two new pitchers for the next season"
approve and express assent, responsibility, or obligation; "All parties ratified the peace treaty"; "Have you signed your contract yet?"
the fourth sign of the zodiac; the sun is in this sign from about June 21 to July 22
a small zodiacal constellation in the northern hemisphere; between Leo and Gemini
(astrology) a person who is born while the sun is in Cancer
any malignant growth or tumor caused by abnormal and uncontrolled cell division; it may spread to other parts of the body through the lymphatic system or the blood stream