1. (adjective) engaged in or accustomed to close observation

• alert

2. (adjective) experiencing or accompanied by sleeplessness

• insomniac
• sleepless

1. (adjective) engaged in or accustomed to close observation

• argus-eyed
• open-eyed
• vigilant
• wakeful
• fly
• heads-up
• wide-awake
• lidless
• sleepless

2. (adjective) experiencing or accompanied by sleeplessness

• awake

1. (adjective) engaged in or accustomed to close observation

• awake
• lively
• wary

1. (adjective) engaged in or accustomed to close observation

• alert
• qui vive
• alertness
• on the qui vive
• sharp-sightedness
• alertness
• vigilance
• wakefulness
• watchfulness
• vigilance
• watchfulness
• weather eye

2. (adjective) experiencing or accompanied by sleeplessness

• sleeplessness
• wakefulness

1. (adjective) engaged in or accustomed to close observation

• unalert
• unvigilant
• unwatchful