The Meaning of “~” in Definitions The symbol “~” appears in many definitions. What does it mean? 
Examples:

2   纯；专：专～。～心～意。


https://www.zdic.net/hans/%E4%B8%80



1   头的前部，脸：脸～。颜～。～目。～～相觑。 


https://www.zdic.net/hans/%E9%9D%A2



2   旧时指读书人：～子。～民。学～。


https://www.zdic.net/hans/%E5%A3%AB



UPDATE:
And, what does it mean when there are two consecutive swung dashes? Such as in:  “～～相觑。”
The use of this swung dash means the entry character or word is used in the corresponding words.

2 旧时指读书人：～子。～民。学～。

... is equivalent to:

2 In olden times, refers to educated people. 士子。士民。学士。

This is a common typographical convention, used in many dictionaries globally, including in English.
EDIT: for reduplication or for other forms of repeat of the entry, the swung dash is often repeated, viz for 面

~ ~ 相觑

... is equivalent to

面面相觑.