backscratching
noun/ˈbækskrætʃɪŋ/
/ˈbækskrætʃɪŋ/
[uncountable] (informal, often disapproving)- the fact of giving somebody help in return for help that they have given you, often in connection with something that might be illegal
互开方便之门，互相利用（常指从事非法活动）