lichens

/L AY1 K AH0 N Z/
noun
  1. 1

    Any of many symbiotic organisms, being associations of algae and fungi, often found as white or yellow patches on old walls, etc.

  2. 2

    Something which gradually spreads across something else, causing damage.

    syn:cancer

Synonyms

Source: https://en.wiktionary.org/wiki/lichen, https://en.wiktionary.org/wiki/lichens