There are 2 definitions of fs in English:

fs1

Line breaks: fs

abbreviation

Femtosecond(s).

Definition of fs in:

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Word of the day inamorata
Pronunciation: ɪˌnaməˈrɑːtə
noun
a person's female lover

There are 2 definitions of fs in English:

FS2

Line breaks: FS

abbreviation

(In the UK) Flight Sergeant.