名詞 prophylactic:

1. remedy that prevents or slows the course of an illness or disease
   同義詞：preventive, preventative
2. contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse
   同義詞：condom, rubber, safety, safe

形容詞 prophylactic:

1. capable of preventing conception or impregnation
   同義詞：contraceptive, antifertility
2. tending to ward off- Victor Schultze
   同義詞：cautionary, preventive
3. preventing or contributing to the prevention of disease
   同義詞：preventive, preventative

1. A prophylactic agent, device, or measure, such as a vaccine or drug.
   預防劑預防性的物質、器具或措施，比如疫苗或藥物

pro.phy.lac.tic

adj.（形容詞）
Acting to defend against or prevent something, especially disease; protective.
預防的：防范或預防某物的，比如疾病；保護性的
n.（名詞）
A prophylactic agent, device, or measure, such as a vaccine or drug.
預防劑：預防性的物質、器具或措施，比如疫苗或藥物
A contraceptive device, especially a condom.
避孕工具：預防懷孕的器具，尤指避孕套

來源：
French prophylactique
法語 prophylactique
from Greek prophulaktikos
源自 希臘語 prophulaktikos
from prophulassein [to take precautions against]
源自 prophulassein [對…提防]
pro- [before] * see pro- 2
pro- [有…之前] *參見 pro-2
phulassein [to protect] from phulax [guard]
phulassein [保護] 源自 phulax [守衛(wèi)]

【引伸】
pro.phylac.tically
adv.（副詞）