It’s one of the most underrated sins, and one that sneaks into office Christmas parties and family gatherings as readily as that extra glass of eggnog.

Gossip: It may seem innocuous compared to theft, murder, adultery. And when defined as trivial talk, it’s typically harmless. But when it involves inappropriate or uncharitable conversations about those who are not present, it is sinful.

“It’s so rotten, gossip,” said Pope Francis during a Sunday Angelus in 2014. “At the beginning, it seems to be something enjoyable and fun, like a piece of candy. But at the end, it fills the heart with bitterness and also poisons us.”

The pope regularly challenges the faithful to eschew gossip, as do many of the saints. St. Thomas Aquinas, with his typical thoroughness, breaks down several forms of gossip in his treatise on justice.

He discusses backbiting, or secretly and quietly talking behind someone’s back. A person is not present to defend or clarify what is said. And then there’s derision, or making fun of a person —their mannerisms, a physical trait or personal quality. While some of it can be lighthearted, it often veers into hurtful or demeaning.

It is easy to convince ourselves that speaking about someone else in unloving terms is not all that bad, but it is spiritually corrosive.

The Catechism of the Catholic Church includes gossip under its discussion of the Eighth Commandment, “You shall not bear false witness against your neighbor.”

When the temptation to gossip arises, let’s do as Pope Francis suggests and bite our tongues. “You might harm your tongue,” he said, “but you won’t harm your brother or sister.”