This is the 715th most frequent Japanese word.
トロ
"トロ" (toro) refers to fatty tuna, specifically the tender, fatty portion of the tuna belly often used in sushi and sashimi.
Here, 'トロ' refers to the fatty part of tuna, commonly associated with sushi.
この寿司は新鮮なトロが使われています。
This sushi is made with fresh fatty tuna.
In this usage, 'トロリ' (adverb form of トロ) conveys a mellow or viscous shining, describing something smooth and fluid-like.
昨日の晩は月がトロリと輝いていました。
Last night, the moon was shining mellowly.
In this sentence, 'トロい' is an adjective meaning sluggish or slow-paced, showing a colloquial extension of the word's meaning into describing a person's actions.