• (p. pr. & vb. n.) of Observe • (a.) Giving particular attention; habitually attentive to what passes; as, an observing person; an observing mind. Found on http://thinkexist.com/dictionary/meaning/observing/
Ob·serv'ing adjective Giving particular attention; habitually attentive to what passes; as, an observing person; an observing mind. -- Ob*serv'ing*ly , adverb Found on http://www.encyclo.co.uk/webster/O/5