In fact, if you search "entrism" on the Web, you get dozens of answers about Trotskyites.
According to my dictionary, "subversion" is
n 1: activity aimed at bringing about an overthrow of a legally
constituted government [syn: {subversive activity}]
2: the act of overthrowing a legally constituted government
but here the idea is not to overthrow a government (or at least, very indirectly), but to infiltrate a political organization (such as another political party). David.Monniaux 23:19, 21 Sep 2003 (UTC)
[1] may shed some light on Troskyite entrism. Maybe I should mention the PT's entrism into FO. David.Monniaux 23:28, 21 Sep 2003 (UTC)