I want to pursue M.S. from USA. I know that it is required to have a background of publishing technical papers for getting admit in a good University. But I wanted to know whether is there anything else apart from publishing a paper that constitutes as "Research" by the Admission authorities? Thank You.
A senior thesis (or, if you're engineering, your senior project, if you did one) would probably be a good thing to showcase, as it demonstrates both your ability to perform work in a group as well as your ability to write.
Internships are great. They show that you can work and it also can serve as a reference.
If you've done anything else particularly notable (e.g., won a nationally recognized science fair), you can mention it, but the number of people who've done stuff like this is pretty miniscule.
From your question, it is not clear that what MS do you referring to and seeking advice for. If you plan for MS by course, the admission committee do not usually evaluate you based on publications, because they don't need you to do research and therefore, it is not needed. They are looking for the university from which you did your UG, your marks, and your final project TITLE and your work.
If you are after MS by research, the story is slightly different, but still publication is not the only requirement. I guess, it is okay to have UGs without publications since UGs are busy with large number of subjects to take (depends on the universities they study) and CS is one of the majors that needs mini project for majority of subjects. Hence, you may not have enough time to be exposed to the research and publication, especially if your university does not approve research project as final project.
For MS by research, the main piece of evidence to show you know research is to prepare a very impressive research proposal. If you can impress them, you have the position. Sometimes looking at recommendation letter also works. If you have a good rec letter with some research-based recommendations and the admission committee know the person issued the recommendation letter, it may change their idea and cover some of your weaknesses. Also, doing vulonteer job is also important to demonstrate your ability to work in a new domain with different people in a team or as an individual.