The American Sign Language sign for "insure" or "insurance" is generally done by
a slight shaking of a palm forward "I" hand from side to side.
The general sign for INSURE or INSURANCE:
INSURANCE (animated gif)
Notes, references, and/or samples:
The ASL sign INSURANCE can also be used in context to mean "infection."
The meaning can be made more clear by using a facial expression that matches
your intent. Generally the concept of "infection" would use a concerned or
somewhat distressed facial expression. You do not always have to use a lot of
facial expression with the sign INFECT or INFECTION since it is possible to
discuss infection dispassionately. (For example, medical students or
doctors might be jaded about "infection.") Dispassionate means "not
influenced by strong feeling."*
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*Reference:
"dispassionate." Merriam-Webster Online Dictionary. Web. 26 Oct 2019
<http://www.merriam-webster.com/dictionary/dispassionate>.