There are 13 11-letter words that start with 'mag'.
| magazinists | magisterial | magisterium | 
| magistrally | magistrates | magnanimity | 
| magnanimous | magnetising | magnetizers | 
| magnetizing | magnificats | magnificent | 
| magnificoes | ||
Note: These 13 11-letter words that start with 'mag' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with magn, magi, maga, magd, mage, magm, magg, magu, magl, mago, magp, mags.
4-letter words start with 'mag' (3)