3drealms says this as the release date for Duke Nukem Forever.

1. noun. It is the sudden feeling of an inexplicable joy one gets when something romantic or idealistic occurs.

When kilig, one may experience the following:

*butterflies in one's stomach
*heart melting
*shivers down one's spine
*irrepressible noises from one's mouth
*uncontrollable smiling
*an inner conflict between hope of something wished for and reality

Kilig may also be defined as that mountain top, floating, on cloud nine, invincible, i-could-keep-smiling, heart aching goodness and feeling which overpowers the mind's ability to think straight, act straight, breathe properly and articulate thoughts into a single comprehensible sentence.

Originally used by 3D Realms as the "release date" for the game Duke Nukem Forever, it basically just translates to either "we don't know yet" or can be jokingly used in the context of indefinitely delayed/Early Access games.