ADVISER
adviser, advisor, consultant
(noun) an expert who gives advice; “an adviser helped students select their courses”; “the United States sent military advisors to Guatemala”
Source: WordNet® 3.1
Etymology
Noun
adviser (plural advisers)
one who advises
Usage notes
• In the UK, Ireland and Asia the spelling is traditionally adviser, though US spelling advisor is becoming increasingly common. In the US, Associated Press style is adviser, and most newspapers and some magazines follow that spelling, whereas US federal government style, other government agencies, and many businesses prefer advisor. News organizations around the world may change spelling found in sources, even in quoted material. US book publishers may be less likely to change spelling in quoted material because this practice is contrary to The Chicago Manual of Style.
Source: Wiktionary
Ad*vis"er, n.
Definition: One who advises.
Source: Webster’s Unabridged Dictionary 1913 Edition