1. 瞄准：side-well neutron logger 井壁中子测井仪 | sighting 瞄准 | sighting device 粗瞄准器

2. 视线：sight glass 窥视镜 | sighting 视线 | sign 符号

3. 照准：sight line 视准线 | sighting 照准 | sighting device 照准装置

4. 检验;观测：sighting vane 瞄准器 | sighting 检验;观测 | sightseeing launch 游览艇

noun

1. the act of observing

e.g. several sightings of enemy troops were reported