al-pref. Variant of ad-..American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.al- var. of ad- before l: allure. -al1 , a suffix with the general sense ?of the kind of, pertaining to, having the form or character of? that named by the stem, occurring in loanwords from Latin (autumnal; natural; pastoral), and productive in English on the Latin model, usu. with bases of Latin origin (accidental; seasonal; tribal). Compare -ical, -ar 1, -ial. [