( ( A tsunami ) ( ( is ( ( a ( sea wave ) ) ( caused ( by ( ( ( an ( underwater ( ( earthquake or ) landslide ) ) ) ( -LRB- ( ( usually ( triggered ( by ( an earthquake ) ) ) ) -RRB- ) ) ) ( displacing ( the ( ocean water ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN tsunami)) (VP (VBZ is) (NP (NP (DT a) (NN sea) (NN wave)) (VP (VBN caused) (PP (IN by) (NP (NP (DT an) (JJ underwater) (NN earthquake) (CC or) (NN landslide)) (PRN (-LRB- -LRB-) (VP (ADVP (RB usually)) (VBN triggered) (PP (IN by) (NP (DT an) (NN earthquake)))) (-RRB- -RRB-)) (VP (VBG displacing) (NP (DT the) (NN ocean) (NN water)))))))) (. .)))
A tsunami is a sea wave caused by an underwater earthquake or    landslide (usually triggered by an earthquake) displacing the ocean water.
(ROOT (S (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN underwater) (NN earthquake)) (VP (VBZ creates) (NP (DT a) (NN tsunami))) (. .)))