There are 16 words that start with 'slac'.
| slack | slacks | slacked |
| slacken | slacker | slackly |
| slackens | slackers | slackest |
| slacking | slackened | slackener |
| slackness | slackeners | slackening |
| slacknesses | ||
Note: These 16 words that start with 'slac' are found from the USA & Canada version of the tournament Scrabble word list.