prophylactic
US /ˌproʊ.fɪˈlæk.tɪk/
UK /ˌproʊ.fɪˈlæk.tɪk/

1.
intended to prevent disease
:
•
The doctor prescribed a prophylactic antibiotic to prevent infection.
•
Wearing a mask can be a prophylactic measure against airborne diseases.
1.
a medicine or treatment designed to prevent disease
:
•
He takes a daily prophylactic against malaria.
•
The vaccine acts as a powerful prophylactic.