acicular
adjective
acic·u·lar ə-ˈsi-kyə-lər 
: shaped like a needle
acicular leaves
acicular crystals
Word History
Etymology
borrowed from New Latin aciculāris, from Late Latin acicula, acucula "small needle, small pin for a headdress" (from Latin acu-, stem of acus "needle" —going back to Indo-European *h₂eḱ-u- "pointed"— + -cula, diminutive suffix) + Latin -āris -ar — more at acute
First Known Use
1709, in the meaning defined above
Medical Definition
acicular
adjective
acic·u·lar ə-ˈsik-yə-lər
: shaped like a needle
acicular crystals