Bullish: your monster is Running Wild while moving forward.
Timidity: your monster is Running Wild while moving backward.
Palsy: effect from Skills with Fire, Ice or Thunder Lore.
Slow: effect from Skills with Water, Wind or Earth Lore.
Addled: effect from Skills with Heart Lore.
Cursed: effect from Skills with Magic Lore.
Composed: movement speed and guts regen increase, but def is reduced. You are also harder to hit. Composed is activated by at least two unanswered attacks in a row. In other words, hit your opponent twice in a row without him getting to hit back and you may become Composed.
Nilvana: may occur when a monster is missed 3 times in a row, causes opponent's hit % to be lowered significantly.
Final Guts: the monster comes back to life and gains 1 Life point per 100 Life points.
Guard: reduces damage received from attacks.
Confused: your monster is more likely to run wild.
Fury: Happens after your monster's been hit (not necessarily for a large amount of damage). Seems it ups your critical ratio.
Force: Occurs after a successful counter.
Real:
Seal: Happens after a succesful counter. The skill range of the countered monster where the seal happens will not be useable for a moment.
Caution:
Barrier:
Poison:
Maximize: result of the Combination Skill from a Fancy monster.
Thanks to John Hawley, Trickster, Harrabcat, Infernus, Lisa Shock, Tjmax, TheUltimateEnd, TheSillygoth