Definify.com

Webster 1913 Edition

Noun.

The process of the first growth of teeth, or the phenomena attending their issue through the gums; dentition.

ppr.

Breeding teeth; undergoing dentition.

Noun.

The operation or process of the first growth of teeth, or the process by which they make their way through the gums, called dentition.

teething ‎(countable and uncountable, plural teethings)

The eruption, through the gums, of the milk teeth; dentition.
- 2009, Katie Van Dyke, Unlikely Truths of Motherhood
  But with night feedings and night teethings, often the greatest challenge of all for a young mother is simply fatigue.

eruption of milk teeth

teething