May one wish a merry Chris-mas, or happy holidays, to a gentile acquaintance or neighbor?
Merry chris-mass: The term Chris-mas is not to be mentioned, due to the prohibition against mentioning the name of idols.
Other greetings: It is forbidden to enter the home of an idolater on the day of his Holiday and wish him Shalom/peace. If one found the gentile outside of his home, he may greet him with a low voice and melancholy demeanor. [Some Poskim rule the above prohibition only refers to using the word “Shalom” being that it is the name of Hashem, however, one may greet him using other terms. Practically, if the gentile does not believe in the religious connotations behind the holiday, then there is no prohibition to mention to him “Happy Holidays.” If, however, the gentile believes in the idolatry related content behind Christmas, seemingly, one may only do so in a pressing situation, to avoid enmity.
 Michaber 148:9; Gittin 62b
 Bedek Habayis in name of Orchos Chaim, brought in Shach 148:7; The Shach however leaves this matter in question
 Michaber 148:5 regarding presents; Avoda Zara 65a
 See Rama 149/12; Terumos Hadeshen 195