LAGOS—Nigeria is beating the West at its own word game, using a strategy that sounds like Scrabble sacrilege.

By relentlessly studying short words, this country of 500 languages has risen to dominate English’s top lexical contest.

Last November, for the final of Scrabble’s 32-round World Championship in Australia, Nigeria’s winningest wordsmith, Wellington Jighere, defeated Britain’s Lewis Mackay, in a victory that led morning news broadcasts in his homeland half a world away.

It was the crowning achievement for a nation that boasts more top-200 Scrabble players than any other country, including the U.K., Nigeria’s former colonizer and one of the board game’s legacy powers.

“In other countries they see it as a game,” said Mr. Jighere, now a borderline celebrity and talent scout for one of the world’s few government-backed national programs. “Nigeria is one of the countries where Scrabble is seen as a sport.”