（为了改变某政党的原则和计划）打入某政党内部的行为the process or policy of members of a political group joining another party or group with the intention, often secret, of changing its principles and plans
Their strategy was to infiltrate the Labour party - a Trotskyist technique known as "entryism".
The RSPCA claimed it was the victim of entryism. RSPCA声称自己是渗透主义的受害者。