请问security是什么意思

[美] [sɪˈkjurətɪ] [英] [siˈkjuːriti] 名词安全,安全感[不可数名词]Two guards looked after the security of the property. 两个警卫看管财产的安全。证券,债券[P]He traded in securities and became rich. 他做证券交易发了财。保证;保障;担保(品)[不可数名词][可数名词]A life-insurance policy may serve as security for a loan. 人寿保险可作贷款的抵押。

1、防备,保安;防护,防御(措施)[不可数名词][可数名词][(+against/from)]They tightened security during the President's visit. 他们在总统访问期间加强了安全防卫。