1. [adv]  in the original or natural place or site; "carcinoma in situ"; "the archeologists left the pottery in place"
2. [adj]  being in the original position; not having been moved; "the archeologists could date the vase because it was in situ"; "an in-situ investigator"

IN-SITU is a 7 letter word that starts with I.

1. \In` si"tu\ [L.]
   In its natural position or place; -- said of a rock or
   fossil, when found in the situation in which it was
   originally formed or deposited.
   
   

2. \In si"tu\ [L.]
   In its natural or original position or place; in position; --
   said specif., in geology, of a rock, soil, or fossil, when in
   the situation in which it was originally formed or deposited.
   
   

1. Refers to performing assays or manipulations with intact tissues.
2. archaeological items are said to be "in situ " when they are found in the location where they were last deposited.