Refers to the emotion of jealousy or envy, often in a psychological or descriptive context. 嫉妬 (しっと) alone is more common in everyday speech; 嫉妬心 emphasizes the feeling as a noun.
Compound of 嫉妬 (しっと, 'jealousy') and 心 (しん, 'heart/mind'). The exact historical derivation is uncertain, but the combination straightforwardly means 'jealous heart' or 'feeling of jealousy'.