It’s an adverb that can be used in a number of different ways:
1 It can mean particularly savage and violent;
2 It can mean in a direct and uncompromising way, where no attempt is made to disguise unpleasantness;
3 It can mean to an extremely unpleasant or harsh degree;

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.