My wife confesed to me that she cheated on me by kissing another man. Can this be considered committing adultery?

In and of itself, mere kissing, without more contacting does not rise to adultery in the State of New York for purposes of obtaining a divorce. It usually needs to be intercourse or oral or anal sex in order for adultery to be found. Now, if the kissing became more intimate but did not technically rise to the level described above, it would be in the discretion of the Judge as to whether sexual contact was made. However, if you wanted to use the kissing as a grounds for divorce, you could clearly claim that this was part of cruel and inhuman treatment that caused great embarrassmnet and humiliation that made it unsafe and improper for you to continue to live as husband and wife

This would be a question for the court.  Why don't you check out the definitions below.

 §  170. Action for divorce. An action for divorce may be maintained by
  a husband or wife to  procure  a  judgment  divorcing  the  parties  and
  dissolving the marriage on any of the following grounds:
4) The commission of an act of adultery, provided that  adultery  for
  the  purposes  of articles ten, eleven, and eleven-A of this chapter, is
  hereby defined as the commission of an act of sexual  intercourse,  oral
  sexual  conduct  or  anal  sexual  conduct, voluntarily performed by the
  defendant, with a person other than the plaintiff after the marriage  of
  plaintiff  and  defendant.  Oral  sexual conduct and anal sexual conduct
  include,  but  are  not  limited  to,  sexual  conduct  as  defined   in
  subdivision  two  of  section  130.00  and  subdivision three of section
  130.20 of the penal law.

§ 130.00 Sex offenses; definitions of terms.
    The following definitions are applicable to this article:
    1.  "Sexual  intercourse" has its ordinary meaning and occurs upon any
  penetration, however slight.
    2. (a) "Oral sexual conduct" means conduct between persons  consisting
  of  contact  between the mouth and the penis, the mouth and the anus, or
  the mouth and the vulva or vagina.
    (b) "Anal sexual conduct" means conduct between persons consisting  of
  contact between the penis and anus.
    3. "Sexual contact" means any touching of the sexual or other intimate
  parts of a person not married to the actor for the purpose of gratifying
  sexual  desire of either party. It includes the touching of the actor by
  the victim, as well as the touching of the victim by the actor,  whether
  directly or through clothing.
    4.  For  the purposes of this article "married" means the existence of
  the relationship between the actor and the victim as  spouses  which  is
  recognized by law at the time the actor commits an offense proscribed by
  this article against the victim.
10.  "Sexual  conduct"  means sexual intercourse, oral sexual conduct,
  anal sexual conduct, aggravated sexual contact, or sexual contact.