A word or lexical unit which is dependent for its meaning on reference to some other part of the context, for example a pronoun or the verb do in she likes chocolate and so do I.
〔语言学〕代替形式（如代词或she likes chocolate and so do I 中的动词do）
Definition of pro-form in US English:
pro-form
nounˈprōfôrmˈproʊfɔrm
Linguistics
A word or lexical unit that is dependent for its meaning on reference to some other part of the context or sentence in which it occurs, for example, a pronoun replacing a noun or noun phrase, or a verb replacing a clause, such as do in she likes chocolate and so do I.
〔语言学〕代替形式（如代词或she likes chocolate and so do I 中的动词do）