Here are two ways to do it:
#[
#show terms: it => {
show strong: it => emph(it.body)
it
}
/ Term1: The explanation
/ Term2: The explanation is longer this time
]
#[
#show terms.item: it => {
emph(it.term)
terms.separator
it.description
linebreak()
}
/ Term1: The explanation
/ Term2: The explanation is longer this time
]
Based on How to change the appearance of the terms in a term list? - #4 by SillyFreak