Cotton in which the thickening of the fibre wall is appreciably less than usual.
Note. If growth conditions are not favourable, possibly as a result of attack by disease or through plant senility, or occasionally because of the genetic nature of the variety, the secondary-wall thickening may first be delayed and then proceed at a reduced rate or wall development may cease prematurely: the ripened boil will contain a high proportion of developed immature fibres
also termed unripe cotton
see also dead cotton, mature cotton, motes
Textile Resource (http://www.textile.org.uk)