What is it?

LAUGHING has it, but not CRYING.
HIJACK has it, but not TERRORISM.
FIRST has it, but not SECOND.
AFGHANISTAN has it, but not TAJIKISTAN.
CALMNESS has it, but not NOISE.
DEFINE has it, but not DECIDE.

What is it?

3 consecutive letters of the alphabet.

Originally posted by luskin
3 consecutive letters of the alphabet.

Correct

Starstudded has it to the extreme!

Overstuffed Understudy!