The Greek deponent verb splanchnizomai (σπλαγχνίζομαι) means to feel compassion or to be moved with pity in one's innermost being. It derives from splanchna (intestines/bowels) — the ancients located deep emotion in the gut. It appears 12 times in the NT, mostly in the Synoptics.
Splanchnizomai is almost exclusively used of Jesus in the Synoptic Gospels — it is His characteristic word for compassion. He was moved with compassion (esplanchnisthe) seeing the crowds like sheep without a shepherd (Matthew 9:36; 14:14); healing the lepers (Luke 17, Matthew 8:2–3); feeding the 4,000 (Matthew 15:32). The father in the parable of the Prodigal Son 'saw him while he was still a long way off and was filled with compassion' (esplanchnisthe, Luke 15:20) — the only non-Jesus use in the Gospels, but deliberately depicting the Father-heart of God. This is not a detached pity but a gut-wrenching, all-consuming compassion that moves to action. Jesus never felt splanchnizomai and did nothing. Compassion is active.