to cool less than necessary for a given process or purpose
b.
to supercool
2. Metallurgy
to cool (molten metal) without forming crystals to a temperature below that at which crystallization normally takes place
Metal must be absolutely still to be undercooled
Word origin
[1900–05; under- + cool]This word is first recorded in the period 1900–05. Other words that entered Englishat around the same time include: clone, decompression, desensitize, hydroplane, internshipunder- is a prefixal use of under, as to indicate place or situation below or beneath (underbrush; undertow); lower in grade or dignity (undersheriff; understudy); of lesser degree, extent, or amount (undersized); or insufficiency (underfeed)