vaping

noun

the use of e-cigarettes or other devices that let you breathe in nicotine or other drugs as vapor rather than smoke

The inhaling of a vapor created by an electronic cigarette; the use of an electronic cigarette.
“He went vaping with me last night.”
“These [putting feet on seats and leaving rubbish behind] are officially among the worst habits revealed by staff working on Northern's trains and at stations. Other bugbears include playing music through loudspeakers, not giving way to passengers getting off the train and actually illegal activities such as fare evasion and vaping in enclosed spaces. The list of misdeeds was released by the operator on March 3 to coincide with Employee Appreciation Day.”