General English

General Science

  • noun a stoppage in a process or mechanism due to a fault
  • verb to stop working because something is causing a blockage


  • verb to cause moving parts to become locked and unable to be moved


  • A fruit preserve made by mixing fruit or boiling it with sugar and water and adding extra gelling agent if required, usually pectin. The high sugar concentration inhibits but does not totally prevent proliferation of microorganisms, so jam is usually bottled hot in sterile jars with a seal, or sterilized after bottling.

Information & Library Science

  • verb to interfere with a radio or electronic signal so that it cannot be received clearly

Media Studies

  • noun a device for preventing a pre-recorded videotape from being copied
  • noun a situation where radio or television signals are blocked
  • verb to prevent the reception of a radio or television signal by broadcasting other signals on the same frequency
  • verb to adjust or adapt something such as a pre-recorded videotape, to prevent it from being copied


  • verb to block the enemy’s radio transmissions by causing interference
  • verb to stop firing because of a mechanical failure


  • noun a car. A shortened version of jam jar used by younger speakers since 2000.
  • verb to take part in a wild celebration, to ‘party’. An extension of the original musical sense of the word.
  • verb to have sex (with). This vulgarism usually occurs in the form ‘jamming’, and is heard typically among adolescents. Slang uses of the word jam as verb or noun play on its standard sense of crush(ed) or wedge(d) together. The additional sense of sweet confection also influences the use of the word in sexual euphemisms.
  • verb to move quickly, leave hurriedly. This sense is of uncertain origin, but may refer to jamming the foot on the accelerator.
  • verb to sniff cocaine. This use of the word presumably refers to jamming the substance up one’s nose. It may alternatively refer to jam as something sweet.

Origin & History of “jam”

The verb jam, meaning ‘press tightly together’, first appears in the early 18th century (the earliest-known unequivocal example of its transitive use is in Daniel Defoe’s Robinson Crusoe 1719: ‘The ship stuck fast, jaum’d in between two rocks’). It is not known where it came from, but it is generally assumed to be imitative or symbolic in some way of the effort of pushing. Equally mysterious are the origins of jam the sweet substance spread on bread, which appeared around the same time. Contemporary etymologists were nonplussed (Nathan Bailey had a stab in the 1730s: ‘prob. of J’aime, i.e. I love it; as Children used to say in French formerly, when they liked any Thing’; but Dr Johnson in 1755 confessed ‘I know not whence derived’); and even today the best guess that can be made is that the word refers to the ‘jamming’ or crushing of fruit into jars.