| Adv. | 1. | thoughtlessly - in a thoughtless manner; "he stared thoughtlessly at the picture" Synonyms: unthinking, unthinkingly Antonyms: thoughtfully - in a thoughtful manner; "he stared thoughtfully out the window" |
| 2. | thoughtlessly - showing thoughtlessness; "he treated his parents thoughtlessly" Antonyms: thoughtfully - showing thoughtfulness; "he had thoughtfully brought with him some food" |