"Tardiest" is an adjective that refers to someone or something that is late or slow in arriving or completing a task. Synonyms for this word include "slowest", "latest", "behind schedule", "delayed", "procrastinating", "sluggish", "leisurely", "dilatory", "belated", "deferred" and "lagging". While these words all have similar meanings, some may be more appropriate than others depending on the context. For example, "belated" is often used in reference to a missed or delayed deadline, while "sluggish" may be more appropriate when referring to a slow-moving individual or group. In any case, these synonyms can be useful for expressing various shades of meaning related to tardiness.