In modern linguistics new developing approaches to synonymy are based on descriptive man-oriented techniques of a synonymous field modeling. The idea of classic semaciology that word semantics (meanings) is limited led to numerous discussions to find a limit number of synonyms. But later linguists began to think that word semantics is diffusive and can't be defined categorically and this is a language natural feature. This article describes how the synonymous field of Russian lexis is organized, with this account basing on the indexes of the semantic proximity between synonyms, these data being found out within associative experiments with Russian native speakers. In our study the description of the synonymous space organization is based on the following provisions: 1. Synonyms are similar like one family members, they have a family resemblance. 2. "Stimulus-response" pairs in the association experiment are considered to be microsituations, proposition elements (Yu. Karaulov), presenting a set of possible situations, typical of this or that lexeme functioning. The associative field is regarded as a propositional network. 3. The synonyms field has an internal organization, which is based on the "word-theme" (N. S. Novikova, G. A. Martinovich). 4. A synonyms family is a field structure, having a vague, diffuse boundaries and it is incomplete and unfinished on principle. 5. Synonyms are included in the native speakers verbal associative network where they are not isolated from each other but relate with other network members, overlap or cross them (i.e. with other synonyms, antonyms, homonyms, paronymy, between which the borders are indistinct). 6. There is always an opportunity that speakers cannot understand synonyms, like any other words. Agnonymy has ontological and epistemological foundation. Agnonymy determines permeability, diffusivity of borders between words meanings, providing links and transitions between words, their functioning in the field space. To conduct the associative experiment 15 groups of synonyms were selected. These units included the words that have been discussed in detail in this article. The degree of these words-synonyms similarity has been defined as the ratio of identical lexical reactions to the total number of associations provoked by stimulating words and amounts 83%. Comparison of associative fields of words that are close in value, showed that the synonyms on the basis of family resemblance in form the space of associative semantic network, where they are at a minimum distance from each other, and which, like the rest of the associative-semantic net is a structure with diffuse boundaries.