(physics) The jagged line, on a chart showing the number of protons and neutrons of all known isotopes, beyond which neutron-rich nuclei are unstable and emit neutrons.

(ice hockey) A pass across two of the three lines dividing the rink, the center red line and the two blue lines. Under some rules such a pass is illegal.

(idiomatic) At some point in a process or in a series of events; at some unspecified or unknown time; eventually.

A short introduction or comment intended to garner romantic or sexual interest from a stranger.

(UK politics) A directive to MPs from party leaders to vote in a particular way in parliament, despite what the MP might believe or what his or her constituents might like.

plural of double yellow line

A symbol in musical notation used to subdivide long measures into shorter segments for ease of reading.

plural of double bar line

plural of dotted bar line

A symbol in musical notation used to separate two sections or phrases of music.