extradosn.拱背(拱洞的外弧面；外拱线)extraadj.额外的n.额外之物；临时演员adv.特别地extra white cotton特白棉extravasation rate电解质外渗率extraposition list外置表extra thin noodles特细面extracellular face外胞半单位膜面extra pseudo order补充假指令,附加假指令extra high potency超高效能extra high tension特高压Extra-heavy rain大暴雨extra-duty glaze特种釉