Noun
a member of a clandestine subversive organization who tries to help a potential invader
Source: WordNetWe will liquidate the kulak, but not because he is a kulak but because he is a fifth columnist ... The present struggle is national liberation in form, but class war in essence. Josip Broz Tito
Any challenge or criticism of some his warped policies or naked corruption going on in government you are tagged a fifth columnist and unpatriotic. Source: Internet
He alleged that, the claimed outbreak is the handy work of mischief makers and fifth columnist. Source: Internet