Many people first encountered this word, as I did, during a school science lesson in which some crystals were put on the bench. Within a few minutes, as the result of being hygroscopic, they absorbed enough water vapour from the air to dissolve into solution. Such crystals are said to deliquesce or to be deliquescent.
That’s a specific technical application of a word whose meanings in English are intriguing. For example, how about dusty and deliquescent? In the nineteenth century, deliquescent was used jokingly of someone who has become so hot as a result of physical exertion that he’s swimming in sweat. Dusty and deliquescent became what we may politely call a set phrase or, impolitely, a cliché:
The country pedestrians, “dusty and deliquescent” with their long rounds, are seen marching back towards the city.
The Little World of London, by Charles Manby Smith, 1857.
The Latin original is deliquescere. This could mean “dissolve”, but more negatively it implied melting away or exhausting. Romans might employ it figuratively for dissipating one’s energies. This produced another English meaning — of organic matter such as fungi that decomposes into a liquid mass after fruiting. Such ideas gave this author a way to create an image of fading fruitfulness:
There was a middle-aged woman at the far side of the room with black dyed hair and a sort of deliquescent distinction.
Room at the Top, by John Braine, 1957.
The word can — surprisingly — describe a plant stem that repeatedly branches. The concept is of a single stem that ramifies by repeated branchings into ever smaller stems until it fades to nothing. This deeply figurative example is presumably borrowing the idea:
This past fall, with the consecutive openings of six “Asian biennials,” the deliquescent 1990s and early-2000s trend toward establishing new large-scale exhibitions in increasingly far-flung locales bore fruit, such as it is.
Artforum, 1 Jan. 2009