Exploration is a type of Search. Exploration is related to Explore. Pioneer is a type of Explore. Pioneer is a synonym of Initiate. 
Steep is a synonym of Plunge. Plunge is related to Toilet. you are likely to find Toilet in/at/on Apartment. 
Search <--IsA-- Exploration <--RelatedTo--> Explore <--IsA-- Pioneer <--Synonym--> Initiate 
Steep <--Synonym--> Plunge <--RelatedTo--> Toilet --AtLocation--> Apartment 