Initialism of ortho-nitrotoluene.
"The laboratory report listed ONT as a hazardous chemical, where the acronym stands for ortho-nitrotoluene."
In plain English: An ont is an old-fashioned spelling of the word onion, which is a vegetable with layers you peel off to eat raw or cook.
"The ont was busy checking in new patients at the front desk."
Alternative form of Ont.
"The flight departed from ONT, which stands for Ontario International Airport."
Abbreviation of LA/Ontario International Airport (IATA code ONT).