What does Judges 14:18 mean?

Under a death threat from her fellow Philistines, Samson's new wife has betrayed him. She has manipulated, wept, and nagged him, demanding he share a secret with her. As soon as he gave in, she passed that secret on to her murderous townspeople (Judges 14:15–17).

Samson had presented a wager to his thirty Philistine groomsmen. The stakes are thirty sets of clothes, and the challenge is to explain a "riddle." Unlike true riddles, however, Samson's mystery is just a personal secret; it's something no one could know and is therefore an unfair trick. His poetic phrasing described the discovery of a hive of bees in the carcass of a lion, a lion which Samson killed through the power of the Lord's Spirit (Judges 14:5–8, 12–14).

The Philistines confront Samson with the answer with little time to spare. The sun is going down on the final day of the feast. They frame their solution in poetic language which mirrors the original challenge. Samson immediately knows how they determined the answer. He posed the wager knowing that there was absolutely no way it could be solved—and only his new Philistine wife was told the secret.

Using yet another turn of phrase, Samson points out exactly how they came to the right answer. His retort is meant as an insult, both to the thirty men for cheating as well as a crude dismissal of his wife. She was nothing but a tool for these men to "dig up" a secret like livestock pulling a plow. Still, referring to her as a "heifer" in this context is as derogatory as calling a modern woman a "cow." It makes crude implications about intellect and ownership. A literal "heifer" is a young female cow, which in Samson's culture was associated with childish stubbornness (Jeremiah 50:11). The phrasing might also be taken as a crude accusation towards the woman's sexual faithfulness.

Thwarted in his attempt to swindle the Philistines, and betrayed by his own betrothed wife, Samson will lash out in rage (Judges 14:19).