The term "icchantikas" is introduced in the handouts for Lesson 6 (p 3), but I do not see a definition.
Here is a brief paraphrasing of the definition provided in the Chinese Buddhist Encyclopedia online.
One who has no interest in the path to Awakening, or one whose good roots are completely covered; those given over to total hedonism and greed; those persons who do not believe in the Buddha, his eternal Selfhood and his Dharma (Truth) or in Karma; those who seriously transgress against the Buddhist moral codes and Vinaya; and [those] who speak disparagingly and dismissively of the reality of the immortal Buddha-nature
While the encyclopedia does not clearly state this and I've not previously encountered this term, it appears that it's related to the Sanskrit atyantika - defined here as "sentient beings [who] lack the characteristics of nirvana and would never attain nirvana."
Any other thoughts or insights would be appreciated.
Kenneth Ch'en
Ch'en, in Buddhism in China, defines icchantikas as "those whose primary interest was in in the gratification of their desires." (p 115)
Icchantika
The expanation given by Wikipedia ( english version ) about Icchantika is quite satisfactory as well