This is the 5162nd most frequent Russian word.
нацистской
The Russian word "нацистской" means "Nazi" or "of the Nazis" (adjective form).
Here, 'нацистской' is used as an adjective describing 'армии', denoting an association with the Nazi ideology or regime.
Мой дедушка воевал против нацистской армии.
My grandfather fought against the Nazi army.
In this sentence, 'нацистской' describes 'идеологии', highlighting opposition to this ideology.
Нацистской идеологии следует сопротивляться.
Nazi ideology should be resisted.
'Нацистской' here modifies 'символике', and again serves to denote association with the Nazi regime.